help me before i upgrade

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Joined: Nov 7 2007

I have got as far as I can with my present system, which is as follows :-
Windows XP
Adobe Cs3 Production premium

Intel cure duo 6400 2.13
4gig ram (though i think its only seeing 2?)
Nvidia geforce 7900 gt/gto
C: 700 gig store my scratch files here
D: 500 raw footage
E: 700 other storage
F: 80 gig software backups
G: 700 gig long term storage

My I.T guy has given me two ways to go

A nvidia quadro cx, adobe cs4 and new motherboard
B SD drives

Will the high powered graphics card improve rendering time for color correction in premier and 3D work in after effects.

I would appreciate your feedback before I spend alot out only to find out i took the wrong option