First of all, did you mean $2,000?
If you ment $20,000, that's nuts for a PC, build a real nice PC for $2,000-$3,000 and use the rest on a car or something.
Second of all, you need to do some work for yourself here, we can help you decide what's best but you need to come up with some kind of configuration yourself for us to have a starting point then we can help.
Third, tell us what it is going to be primairly used for, not just gaming but what games, weather or not you need all kinds of special audio ports, a moniter, speakers, things like that.
Post your configuration and we will help you, but no one wants to sit down and do all the work for someone else.