I bought a Specialized Stumpjumper for my "serious" mountain bike about 10 years ago now, for around $1200. It's a great bike, very light and responsive. I think the main difference between the price range you're looking at will be weight (heavier), and subtle differences in the smoothness of the shifting, quality of the shocks, etc. You'll probably be happy with it, and if you get super-serious about biking, you'll want to do some research anyway before dropping more than that on a better bike.