well if your going to be gaming, then onboard graphics won't do the job. you can pick up some great cards for not much money at the moment, try looking at Nvidia's 7 series and ATI's equivalent which I believe to be the X1000 range...I could be wrong. the X1950 range is the next step up and is nice, although maybe a little on the expensive side for those on a budget. Nvidia have already released their direct X 10 cards which you'll probably be better off ignoring at this moment in time. the sensible thing would be to let the prices go down and wait for games to actually be released designed to use it's technology.
as for the specs, it looks like with a decent graphics card you'll be set for gaming. it looks to me like a prerfectly capable system, you shouldn't have a problem with office work and normal everday usage. although I would say the Core 2 Duo
cpu would be a better choice for running office applications and multitasking. aside from that, you've got a great system there.
One word of advice, make sure you have a sufficient power supply, i recommend at least a 400W, although ideally you want to give yourself a bit of clearence and go higher for any future upgrades you may make, such as that graphics card.
hope this helps.
