upgrade??? for now

Hello all....

my specs

cpu: duo2 @2.53

evga 9800gt 512gb

windows xp

500 gb hd

2gb corsair ram

I want to upgrade the cpu and motherboard down the road...but for now i'm going w/windows 7 64 and a videocard...now I found a evga 550ti for $119 on tiger direct!! I would love a 560ti but its out of my price range

I plan on going to a i5 3gz+ 4-6 gz of ramm also new mb

1: is it worth it?

2: will I see a major boost in games

Thanks

G