I'm assuming you don't have another PSU to try out eh or even a spare crappy vid card?
That'd be the easiest way to check of course.
80+ isn't even that bad, it's 80.5F in my room right now, I have water cooling, BUT I was sporting air when it was these temps and higher at one point and never had such issue.
However if your case has poor flow then that could of course be a contributing factor.
Either swap out PSU's or take the vid card that you think is screwing up on you right now and put it into another computer or a friends computer...if it works properly, I guess you could assume it's the PSU, although if you're seeing garballed images on the screen I'd definitely say vid card first