lol
and a complete toaster
I've yet to find a case that wouldn't basically torch everything inside it with four GPU's running full-out
heck i'm using HP Z800 cases and they can just barely handle running two R9 270x GPU's in them. And all of the optional fans are in there.
for 4-GPU and up configurations, I've heard either milk crates or just custom cases are the way to go.
HP z800 seriously? That's an overpriced case designed for minimum noise not maximum cooling. I had one of those at work. A $99 Antec 900 would be better for a fraction of the price. My gaming rig uses a $300 silverstone RV-02E which has some truly beastly airflow from 3x180mm fans with adjustable RPM. It had no problem with 2xGTX580 running furmark with no gap between them. Not that the case even matters that much when almost all GPUs are designed to exhaust all their hot air externally and nothing else is generating significant heat inside the case and all GPUs are designed to run at 80-90C 24/7. I only get fancy cases for the benefit of CPU overclocking.