Cooling: so the H60 isn't a favorite then? So is the H100 heaps better or is just OK? With air, I was mainly concerned about fan noise? Any good suggestions for air cooler suitable for this build?
My thinking with the 850AX was that I've heard that power supplies start to lose their capacity/efficiency over time, so thought I'd err on the safe side, and also leave some room to power an additional card if needed.
Backup is networked. Good point though, not often thought about.
I actually picked the 550D case as I thought it would be a quiet case - isn't this right? I definitely want a quiet case, even thought it won't be next to others.
Outlander - I'm particularly interested in your comment about the gaming card. I've been reading heaps about the performance of quadro vs the gaming equivalents, and I just can't find anything that definitely says they are worth it. Do you have experience with both types of cards? I'd really like to get some more details here.