I found some reviews for the ibuypower wa550b herehttp://www.walmart.com/catalog/allReviews.do?product_id=23745948
One person mentions that it comes with a 300 Watt power supply. If you ever want to upgrade the graphics card, you'd have to upgrade the power supply also. The GT 630 is a "value" card for "entry level" gaming according to ***Geforce***
. It's probably adequate for most adventure games, though you might have to reduce video options to play something like the latest Sherlock Holmes game.
The GT 630 can come with either 1GB or 2GB of video memory and either DDR3 or DDR5. I suspect the GT 630 in the wa550b is the 1GB version with DDR3 since they're trying to keep prices down. The GT 630 is one of those "rebranded" video cards (a rebranded GT 440 according to ***Wikipedia***
GPUReview doesn't list the GT 630, but they do list the GT 440. Although the GT 630 has more video memory than your old 7900GS, it does not look like a faster card to mehttp://www.gpureview.com/show_cards.php?card1=642&card2=443
If it was me, I'd try to find a configuration at eCollege (or possibly CyberpowerPC) that had a better graphics card and power supply. But if money is tight, the wa550b will work.