As for the TDP stuff, I'm curious if it'll be bios unlockable or require a physical voltage mod. I haven't done a physical card mod in ages, I recall modding some old card to over clock it when further as a teen trying to game on a budget, haha. Definitely good to always consider scalability and future proofing a build if at all possible for sure though. I really like the MSI cards, but I'll see what's available with a 6 pin just in case.
Some have mentioned that you have to plug in the 6-pin connector to get the system to boot even if you don't really need it, so just be aware when you are getting a PSU that it will need those (Modular probably a requirement).
I went with platinum rated PSU for the efficiency of it all, but a newer modular unit was really expensive, so I went this route and haven't had any complaints whatsoever.
All six cards running on JPC are about 350W, and When I was mining Groestl is was a very impressive ~265W if I remember correctly.