Overstock.com is a GREAT place for entertainment centers at a reasonable price.
I use a rather pricey one from one of those nice furniture stores where you can customize everything (Perhaps Bassett? But they're all the same) because it was a gift from my boyfriend's parents when we got our new place. I don't remember the exact price, but we have a 55" that it holds nicely as well as our large receiver, Bluray player, cable box, two X-boxes (Don't ask why two if you're a good person...), a Wii in a fancy cooling dock with the Wiimotes charging on each side, all the games for the systems, and a little water fountain... 'cause why not have a little water fountain?
It's only under the TV and just a little longer than it, a few feet high. If you want more information, I can get you the specifics, but it probably costs the same or more than the TV.