OEM is the best...  They all have the same E-code spec but the lighting
output is vastly different. I suggest you stick with Bosch E-code headlights
but this may prove hard to find..

There is two way to go... cheaper way is just replace those lenses. The
prices on the replacement makes it seem high... that you could have bought
entire headlight assembly with low beam projectors

If you want best lighting, go with Bosch HID setup offered by Bekkers
Import... $1600 is the price to get in this class...

Otherwise, I would go with Depo... Depo is owned partially by Hella but
vastly different in quality. Bekkers' facelift headlight kits made in Taiwan
is Depo... and you can get them 1/2 price on eBay...

Ebay also have different sellers with different brand headlights... I really
have no experience with them so I cannot recommend which one. One thing I
can tell you is H7 bulb is better than other choices and low beam projector
is much better choice than reflector.

Your probably best off with Depo units. for around $280 on ebay.

You are getting a trickle of good info and a great deal of garbage in
response to this question.

The facts are as follows:

-Your '97 E300D is a W210-chassis car. DB put a great deal of thought
(and adequate money) into the engineering of both the halogen and the
HID ("Xenon") headlamps for this vehicle. The only significant
difference with the HIDs on a W210 is that the low beam is wider. This
extra width is visually impressive, but much of it is useless: Envision
a semicircle on the ground in front of your car, with the flat side
touching your front bumper. Let's say this semicircle has a radius of
50 feet, just for illustrative purposes. No matter where on the curved
part of the semicircle an object lies, it is the same distance away
from the car in real terms: 50 feet. But, it's not always the same 50
feet. Could be 50 feet straight ahead, 50 feet straight out to the left
or the right, or anywhere in between, you follow me? Now, the farther
away from "straight ahead" you go (as you turn your head towards the
left or towards the right), the closer the object is to the car in
strictly longitudinal terms.  Why does this matter? Because no matter
how good your reaction time, no matter how good your brakes, beyond a
certain lateral angle off the "straight ahead", if something's going to
run into the road, you *are* going to hit it, because there is simply
not  enough time to react and avoid it. The actual angle varies with
vehicle speed and road conditions, but the point is that in these
situations, the difference between the HID and the halogen headlamps is
that with one, you get a clearer view of what you *will* hit.

In strict terms of safety performance -- again, comparing only these
two specific headlamps, the W210 halogens and the W210 Xenons, both in
stock form, in good condition and properly aimed -- there is no
significant advantage one way or the other. Advice to the contrary is
based on subjective impressions of driving comfort and/or repetition of
advertising claims. (NB there are other comparisons that would not come
out the same way. There are specific HID headlamps that are better than
the analogous halogens, and there are specific halogen headlamps that
are better than the analogous HIDs. The only valid generalization is
that good headlamps are better than bad headlamps.)

-The "upgrade" you are asking about is no upgrade, it is a downgrade.
That is because the projector retrofits you ask about are made only by
Taiwanese or Chinese copycat artists (TYC, Depo, DJAuto and others),
and not by legitimate automotive lighting engineering and manufacturing
firms (such as, amongst others, Hella, Valeo/Cibie, and AL-Automotive
Lighting, which is the result of the merger between Magneti-Marelli
Carello and Bosch's automotive lighting division). These
Taiwanese/Chinese lamps look nifty on the webpage or store shelf, and
even look nifty (to some people's eyes) when installed in the car...for
a few months. Then the inferior materials and build quality show
themselves and the lamps begin to deteriorate. Water and dirt entry and
UV-induced early lens haze are common on the Asian-made lamps. And even
if the lenses and seals hold up, there is little or no optical
engineering that goes into these lights. Their beam performance is weak
at best, dangerous at worst. Counterfeit DOT certification and/or ECE
approval markings are utterly common. Often these lamps fail real tests
very badly. Take a look at these two tests:
http://www.capacertified.org/press/CAPALighting3.pdf
http://www.capacertified.org/press/CAPALighting2.pdf
http://www.capacertified.org/press/CAPALighting1.pdf (summary and
explanation of results)

In a nutshell, these are tests of the Depo/TYC copies of very simple,
low-technology, easy-to-make American-car headlamps. The copies fail
badly in almost every regard (fit, aimability, performance, durability,
environmental resistance). The headlamps on your W210 are considerably
more intricate and difficult to manufacture, optically speaking, than
the simple lamps that failed the test. Doesn't inspire confidence, eh!

-Depo is _NOT_ "partly owned by Hella". A particular vendor of Depo's
knockoff headlamps, mostly for BMWs, fabricated this claim in order to
ease sales of this dreck to owners who rightly insist on OEM,
European-made products. (I'm not going to name this vendor, though I'm
tempted. If anyone wants to guess at it, he operates under a cutesy
name that has several U's with umlauts over them to make him look,
y'know, German and stuff.) Other vendors, including a few MB
specialists, picked it up and ran with this Depo fabrication. It is not
true. Hella is Hella. They make quality OE and aftermarket lamps,
amongst many other parts. Same goes for the other real manufacturers
listed above, and others not listed. Depo, TYC and DJAuto (amongst
other knockoff mills) make nothing but low-bid junk with counterfeit
approval markings. Never the twain shall meet.

-Retrofitment of HID headlamps is possible on your W210. To do it
properly is expensive; the $1400 figure that's been floated in this
thread is in the right neighborhood. Using a so-called "HID kit" to put
Xenons into headlamps intended for halogen bulbs is counterproductive,
dangerous and illegal, see
http://www.danielsternlighting.com/tech/bulbs/Hid/conversions/conversions.html

-If you shop carefully, you can find original-equipment replacement
headlamp assemblies for your '97 at a *reasonable* price. "Reasonable"
does not mean "cheap"; quality costs money, and if you're paying half
the price of an OE headlamp for a knockoff replacement, the money had
to come out of somewhere. Both Bosch and Hella supplied halogen
headlamps for the W210-chassis cars. A Bosch or Hella stockist (there
are many) can supply replacements in a Bosch or Hella box, thus saving
you the MB dealer parts markup.  If you feel the need for more light,
go hit up Candlepower, Inc ( candlepowerinc.com ) for some Osram 65w H7
bulbs. The safety performance of a new/perfect set of the halogen W210
headlamps with a set of the 65w bulbs is measurably better than the
safety performance of a new/perfect set of the HID W210 lamps.

OK...I'll shut up now, and let the ad hype parroting begin.