well for $4500 you can get quite a system, but honestly, why? it still won't play crysis all that well. no computer can. but if you still want to, then:
core i7 965, asus rampage II, 6GB DDR3 1600, 2x 4870x2, velociraptors in RAID.
but honestly, save most of that money for something more useful, or a future computer. no matter how much you spend, just remember it'll be completely outdated within months, if not weeks.