Even if you don't buy from them, crutchfield.com has a database that
gives you a good idea if something will work in your car.  It's not fool
proof, but it's a good place to start.

FWIW the last two car stereos I've bought, and one a friend bought, we
got from them.  The inclusion the installation kits has made up for any
difference in the unit price.  The customer service is better than any
local Big Box store.  I've talked with someone knowledgeable on the
phone sooner than it takes to talk to an idiot in person.

But local independents are worth talking with too.  Especially if you're
paying cash, they're likely to be willing to deal a bit.

But yeah, I agree that having a unit that's cheaper and easier to
update, portable and secure (put it in the trunk away from thieving a-
holes) is better than the aesthetics of putting it in the dash.  Not to
mention when new features come along, it's easier to upgrade.

Look at some of the 'cup holder' mounts or even some of the seat bolt
goose neck mounts.  Ram-mount.com for their catalog, gpscity.com for
pricing.  Also techmounts.com.  I think there was GPS Pal (as seen on
Pitchmen) and some others too.  

A bit of spilt loom helps tremendously with cable management.  If you
don't know what I've referring too, there's some good photos here.
http://cableorganizer.com/wire-loom/
Not a recommendation for a source, I don't know these guys.  They're
just the first thing that came up on Google.  The stuff is available
lots of places - auto parts stores, electronics shops, ad nauseam.

Mark
2008 Jetta SEL
1995 Jetta GLS (sold)