the easiest way to figure out if you can run it is to first get the card, and then go to systemrequirementslab.com. when you go to that site, download the java plugin they ask you to install, and then just click the down arrow on the main site and pick a game. it will tell you if your computer can run it.
if you just want a personal opinion, then i think yeah you could certainly run a lot of the latest games. you'd be better off with a dual core rather than just a pentium 4 single core, but i think it should do the job.