most of the top brands have models in that price range. what features do you want? that is the important question. active? usb? dvd? eq ability? t/a? front panel inputs? there is a lot to consider when you are looking for your own perfect hu.
like he said above. i just ordered a pioneer avh 4000 double din dvd player touch screen, it was $319.00 from sonic electronix on ebay. comes with free wiring harness and they credit you $12.99 towards a dash kit. so i got everything for $357. but you gotta buy a remote for $20 which aint bad.
Kenwood KVT-614DVD, is $699.99 retail, 3 x 5v pre-outs, iPod, DVD, etc. Most flip-outs these days are either real expensive, or real shitty. Jensen, Phase Linear, Valor, Farenheit, Dual, Sumas all make cheap flip-outs, but they're all absolute hunks of shit.
Pioneer 800prs... and the cheap pioneer dvd units dont have sub pre outs which is very stupid.. i think the first model with sub pre outs is 5800 or something like tht i forget which exac one i know i know it was $550 or so
Alpine's flip out single din is very nice if you don't notice everything thats missing. Kenwoods are very nice too and have more to offer than Alpine. If you put more cash into it you can get a much better resolution screen.