Need help and advice with upgrading.

Hey guys, i was so close to buying a 9800gtx+ for my computer

http://h10025.www1.hp.com/ewfrf/wc/prodinfoCategory?lc=en&dlc=en&cc=nz&lang=en&product=3663797

but i was talking to a friend who said i should check my power supply first.. which thankfully i did, cause mines only a 300W.

what kind of powersupply would i need to be able to run that card? im also thinking about getting a new cpu but am not sure whether a quad is worth it, or i should just get a 3ghz core 2 duo.

my other specs are included in that link under "product specs."

im looking to upgrade to be able to play Crysis, call of duty 4 maxed and CSS/TF2/HL2 maxed.

any help is much appreciated, thanks.

dont really wanna spend over 400AUD either. :)

I would recommend this power supply:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006

But you live in Australia right? Newegg doesn't ship there(i don't think). You can probably find the same thing over there though.

The reason I suggest this one is because it is a great power supply. Highest quality one out there. It doesn't get better than Corsair. Plus, if you plan to upgrade later, you'll have enough power to do so. The only concern I have is your case. A lot of pc makers make cases that only fit thier own propreitary psu size. However, I don't know if this is the case with your computer. Just a word of caution. Post back if you have any more questions.