Need Help Building a Gaming Computer!?

Ok,so It's time I built a new Gaming Computer.I have had my Gaming Computer for 5 years now,and well it's obsolete.So I need help on building a new one.Because I have this BIG problem of over doing things.Nothing big really something nice for $2000 or less.I really don't want to spend 12,000 on a Intel Extreme quad core based computer.So if can get some ideas for building a nice Gaming Computer.That would be awesome.