Probably better with a single card, although even that is probably going to be WAY overkill for your CPU.
You are pretty limited in what you can do with a 939 socket -- can't upgrade the CPU to a dual-core or anything that could keep up with a modern video card. You're also stuck on regular DDR RAM, which is going to hold you back as well. I honestly would not spend very much money on this machine and save it for a new one, because there's nothing that will make it fast enough.
If you need to hang on to this machine for a while, most I'd spend is $45 to get an HD 3650, which is about the max upgrade for that system.http://www.newegg.com/Product/Product.aspx?Item=N82E16814131169
Basically, this machine is too old and cannot really be upgraded to do more than play low-intensity games.