i want to get a new cpu so i can play starcraft 2 with high settings.

i have a hp xw4300 workstation with these specs:

pentium4 ht 3,40 ghz
4 gb ddr2 ram
radeon hd 4650
hp motherboard 775 socket

i was able to play the beta without any hiccups at the lowest setting. but for the full game release i want to play it in high quality.

i was thinking of getting a core 2 duo e7500 for 100€ or a e8400 for 160€. im worried if the e8400 is too much for my graphic card? will a e7500 be enough?

another concern i have is my motherboard. even tho its 775 socket i dont think it supports core 2 duo chipset. not really sure. whats a good cheapish motherboard to go with e7500/e8400? dont want to spend more than 60€ for a motherboard

and to the germans whats a good cheap hardware shop?