So what's the problem exactly? Can the PSU and the fan be installed at the same time, or no?
This is exactly why I prefer the Thermaltake cases--even the smallest mid-tower models are nowhere near as cramped as this one is.
Personally, I would cut a blowhole right above the rear of the 5 1/2" bays for a 120mm LED fan, slap a fan grill on there, and remove the 80mm from its too-far-back location and mod it into the sidepanel.
Then I'd just leave the top 5 1/2" open for hiding wires and venting heated air...but that's just me.
Your system is experiencing growing pains...and either you'll have to remove some metal and do a couple of fan mods, or you'll have to just buy a new, roomier case.

I mean...dang. Just look at how far back that blowhole is! It ought to be no further than halfway back; what, did they think having it closer to TDC over the CPU would add some sort of benefit to the design or something?!
But, yeah...if I were determined to get more life from a Dreamer II, I'd simply holesaw the top for a 120mm fan, then move the currently-misplaced blowhole down to a spot under the current side panel fan and mount it there to cool the vid card.
Good luck!