yes at 720p you will able to run - http://www.youtube.com/watch?v=fhodgjCdTcE
i have already said gpu vram like 2gb or 4gb doesnot increase performance.
upto res 1600*1050 - 1gb is enough
from 1920*1080 - 2gb is reccommended
i said gt 630 is way way slower than hd 6670.
it is like this:
gt 630 < hd 6570 < hd 5670 < hd 6670/gt 640 < hd 7750/gtx 650 < hd 7770