As all office apps, you can buy each of them as a single software. Of course, the individual price of each apps in the bundle is lower than the unbundled.
From what I heard of beta testers, VirtualPC is not as fast as ppl were looking for. The 3d card should be supported, but doesn't really improve the overall speed. The only reason to buy the 7.0 version of VirtualPC is the compatibility to G5 processors. But as I mentioned before: this info came from some beta testers some time ago. Maybe they changed a lot by now.