I need a graphics solutions that would allow me to use three monitors, one of which must be HDMI and another that must be VGA or DVI. Unforunately, I can only spend between $120-$150 on it. I'd like it to be something that could support moderate gameplay, say Diablo 3 on close to max settings.
This is a good card that will support the monitors. Eyefinity is going to be the easiest and most cost efficient way to do what you're trying to do. If that doesn't have quite enough juice to run the games the way you need them to be run, the 6870 is another option--though just a tad above your price ceiling.
After talking to my buddy who uses eyefinity, he said you'll have to use the DP. I didn't think you did have to. I apologize for the confusion. The good thing is that you can buy the adapter for the first card mentioned and still be within your budget.
I never saw him say anything but using 3 monitors not that he would be using 1 for gaming and 2 for whatever. So whoever suggested the 2 card solution needs to read better. To power 3 displays at even decent graphics for games you cant get a crappy GPU as was suggested. Even 2 7970s would struggle with some things. So id adivse you get a 670 at least or at least a 7950.