Edit: dang I knew I would forget something, will be doing a fresh win 7 install 64bit I think.
Uses -- mostly web surfing and bumming around, probably video editing. I usually have firefox & chrome running lots of tabs (30 - 50)
Probably reusing a 17" LCD, will also carry a 0.5TB drive for data storage over from old build.
1) Is this thing going to work when I put it togeather?
2) How'd I do in balancing the system (whats the weak link)?
3) Do I need a video card? if so what - does the hyper-crossfire work well?
Hybrid crossfire is pretty much useless, its only useful back on the low end 3xxx series.
What do you play on using the system for? If you intend to game then you will need a discrete video card, if you just intend to do basic browsing then the IGP on the 785G is more than enough. If you list your uses we can help you sort out what you need. I dont see any weak links in that build bit but it might be too much or too little depending on your needs.