Very well written and comprehensive post. Followed.
Side note: Beware of the Asrock anniversary z97 motherboard. I've seen a few posts recommend that for a 6 gpu build but it has 2 AGP ports that are unusable. I know because when I first got into mining that's one of the cards I bought lol. Always make sure you're getting the right number of slots!
I just use any old motherboards. I don't like to build rigs with more than 4 or 5 cards. The z97 motherboards are pretty popular in mining rigs but I think they are overkill really. The cut down cheaper versions are good if you absolutely have to buy new.