I was buying my mountain bike for similar money last year. I could have had a niceish mid level hardtail brand new, or just about any type of bike I fancied on pinkbike.
So I bought a 2 year old rocky mountain slayer, 6 inches of travel all round, nice and light, Sram X7 gearing. It is immense, goes up hills fairly well but goes down like a possessed thing, will keep up with most DH bikes. In short its a perfect do it all bike for me. If I was to buy it new I would have cost me nearly 3 times what I paid.
So go have a scour of the classifieds and keep an open mind, then maybe pick out some that your interested in and we can help pick.
edit: it would also be good if you let us know what type of riding you plan on doing, downhill, enduro, trail centres, cross country, cycle to work?