Video card help

[xJACKTHERIPPERx]

im looking to get a video card and some RAM for my computer. its an HP Pavilion a1730n, its got an AMD athalon 64 X2 dual core processor 4600+ 2.4ghz with 2 gigs of ram (soon to be 4 gigs) runnin the 32 bit version of vista home premium. someone recommended me this video card
http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4473322&CatId=1558
but from what ive seen its not the greatest. im looking to have a good enough system to be able to play games like Fallout 3 on at least medium settings. can anyone suggest a good video card for around as much as $75-80 CDN.
I dont get why theres 512mb cards on that site for like $40, and 1gig cards for as low as $50. Is an expensive 512mb card better than a cheap 1 gig card? Would my system be able to handle a 1 gig card? or should i go for a more expensive 512 card?
I'm willing to buy a new power supply if i need to as well. mines only 300W

 

[cjl]

The quantity of memory isn't the main thing with video cards. A good 512MB card will utterly destroy a bad 1GB card in every way. If you can afford it, the ATI 4670 would be an excellent choice.

http://www.tigerdirect.ca/applications/SearchTools/item-details.asp?EdpNo=4483711&CatId=3670

 

[xJACKTHERIPPERx]

but if i got that i would probly need a new power supply right? and what does the GDDR3 on that card mean? this is actually the card my friend has i think. how well would my system run this card?

 

[rambo117]

no way m8. the computer i built for my dad is has a cheapy ass 400W PSU and has not only a 4670 but a quadcore 810 in it. rock stable

definately go with cjl's recomendation. its a great card and will murder just about anything else in it's price range.

 

[xJACKTHERIPPERx]

well my power supply is only 300W and the card says needs 400W minimum. and does it matter that my comp has DDR2 ram and the card says GDDR3? whats that mean?