if service is what you want....go to crutchfield. Sure their prices are a bit higher then other places on the net, but I still think they are the best out there....here's why:

1. Service....they have great customer service, and a 30 day money back guarentee.
2. Tech support...the provide all the instructions to take your car appart
3. Free harnesses and dash kits....they give you the extra parts to actually get the thing in there....that's about a $20-40 value, plus you don't have to drive to the store.
4. Longevity...this store is going nowhere. They've been in the game longer (or almost as long) as anyone. They are not going to dry up next week and close their doors.
5. Warranty...everything is A-stock and is warrantied.

That's 5 pretty good reasons to go with them. I feel their headunit selection is fairly good for the mainstream. If you want something exotic, then go somewhere else, but for most consumers they have what you are looking for.

Sorry to sound like a salesman, but I think people shop by price only. There is a lot of hidden value to shop with a reputable dealer that some people don't see.