The radiator is one of the few parts on Hondas that folks
here generally say can be replaced with non-OEM without
concern and at a much lower price. Check the archives for
reports of same.

Elle
Original owner, 1991 Civic, second radiator

I purchased a replacement radiator from performanceradiator.com 3
years ago for my 95 Integra. It had a 3 year warranty. Everything fit
perfectly and was great until about 3 months out of the warranty
period it started to leak. Since I was selling the car anyway I opted
to save some money and get a replacement from autozone. Everything fit
in perfectly except for one fan mount. I ended up getting another
radiator from performanceradiator even though I didn't want to, but
had no choice as I needed to put something in. About a month later the
radiator started leaking. After the replacement it has been ok for 5
months until I sold my Integra. If I had to do it again, I would just
buy the OEM one. At least I'm now skilled in pulling them out :)

Others have had better luck at higher quality after market radiators
so they may be able to comment on them.

some of the after-market radiators are very good.  nissen  and visteon
are two i have personal experience with and think they're great value.
but the cheap ones are really not very good and i'd avoid them.

Three years and counting on the replacement for my '90 accord.
Radiator Barn, 85 bucks, free shipping in two days,  everything fit
just right, two hour job.

Frank

Name brand aftermarket rads should work well at a substantial
discount. Modine was a major aftermarket brand and it merged with
TransPro/ReadyRad to become Proliance. The local NAPA store carries
them and with a lifetime warranty.

http://www.pliii.com/

Koyo seems to be another popular brand, the ones with plastic tanks
are now made in Malaysia and one other place; all alumns are made in
Japan. Don't care for Spectrum Premium.

http://www.koyorad.com/products.html

Visteon is actually a Tier-1 supplier to manufacturers, basically a
former Ford subsidiary. AC Delco also reboxes what they (Delphi
subsidiary) don't make. Many Accords come with GM batteries and
alternators, and who knows, may be radiators too. BTW, Toyota buys
from Delphi and gave them an award a few years back:

"Delphi earned Toyota's "Global Contribution Award" for the company's
significant dedication to Toyota's global business development in
2004."

Some of the aftermarket items have lifetime warranty, at half the OEM
price. I've had an aftermarket in my civic for like a decade now, with
no problems; the factory one was inadequate from day 1, to the point
where i thought it was just that civics had undersized radiators.