Thanks so much for all the additional input and suggestions!
I'll try putting in the 3rd card with the 950 and seeing what happens.
I'll likely need to upgrade if/when I OC the cards and really push the 950 though.
Sorry to badger, but does anyone have any thoughts on those accessories I asked about? (Add2PSU, Lian-li, or the auxiliary PSU)?
Like I said, the PSU is only 2 months old haha. Although maybe I could cut my losses by getting like 100ish bucks and buying another one I'd prefer to just add one if it doesn't cause huge problems.
My case I'll be getting has multiple PSU mounts.