Upgrade Advisor is good for an existing machine, but won’t be much help to a set of components. If you’re pulling things out of the old box (including software), it will help with those. Other than that, there’s the manufacture site and communities like newegg, Toms, anandech.
Practically all new components will have Vista 64-bit drivers that should work with 7. The main problem would be with existing components (since it sounds like the upgrade will be piecemeal) and peripherals that the Upgrade Advisor would find.
I just installed Windows 7 last Sunday and it’s great. Took almost 4 hours, though. Pre-loaded would have been better.