The best bike for XC racing is probably not the best model for commuting. Most of us regular riders have a nice bike for play and a cheap, reliable practical bike for work. Commuting can be very hard on bikes and its better if you are not too precious about your mount. Also, you dont have problems with people stealing nice components.

There are loads of great bikes within your pice range, but get one that fits you well. If you pick up a cheap 2nd hand MTB, something like a Specialized Stumpjumper, you can commute on it, and ride it off-road, and get the feel for what you want out of a good bike. You will then know what a good fitting bike feels like.