Sky, I have the same machine. Its easy to upgrade this CPU to 3 Gigs. Just google it.
I have upgraded my original card (same as you I think) with an GTS250. Works great, I think.
EDIT: Sorry, I have the q6600. FOr info check this link:
http://www.ocforums.com/showthread.php?t=546760
Question: Isnt the screen resolution posted in the first post kinda low, and in 4:3?