I would also love the Idea of going 64 bit but you need 4gigs of ram to make it run better than 32 bit, I tried going 64bit on 2 gigs of ram, damn, it was really slow.
see the Dell website and they have many gaming computer models listed there, see the comp sys model number and consult your near store
It's good that you changed the specifications that was vary heavy spec. which are used for server and extreme graphic designing kind of stuff.
I know its already been said, but you wont go far wrong with an i7 based build. Want to know the easy thing to do? Visit a gaming computer website that sell them and copy the spec. Take a look at out site gaming computers and take your pick. Feel free to give me a shout if you get stuck on anything