For office applications, an 8400GS is sufficient. If you want to play any reasonably modern games however, it is hardly better than an integrated graphics chipset (why HVO simply said it sucks). If you're on a tight budget, a HD4670 or HD5570 would be reasonable minimums. If you want to stick to nVidia, a GT240 is the lowest you'd want to consider for games.
Edit: Oh, and Biostar is a budget brand. They aren't "bad," but the warranty will probably be shorter, the quality a little lower, etc. I put a Biostar HD4650 into my non-gamer Mom's PC about six months ago, and it has been fine.