well for the time being you may do with your P4 but then as pathiks said it will be giggest bottleneck and within few months youd have to go for a new processor..
but to play crisis at that settings will be okay because CPU does not play really important role in GFX.. though i think that the AI wont be as good because it needs better physics processing which is handled by the CPU.. and crysis
AFAIK wont be enjoyable at anything lower than the hardest level...
anyways enjoy... but with that config be prepared for a proccy upgrade soon ...
BTW 650i Ultra won't support new 45 nm range isnt it?...
If 650 i does not support 45 nm quad cores then PLEASE go for Biostar P35 as it will be a great VFM 45 nm mobo solution...