I could do 140ea on the 3 MSI's from phillipma, the other 3 cards cost me more so I can't.
I got the limit from trying to run them, possibly a bios limitation...phillipma confirmed it and said he'd had or heard of mixed success with 480's added...ask him if you need specific confirmation of his thoughts on the matter so I'm not paraphrasing.
I was however able to get an Nvidia card to run as a 5th gpu in the build...but not a 5th and 6th...possibly a motherboard limitation.
That's unfortunate. Is that for any kind of 470? I doubt it's a motherboard limitation as, to my understanding, many can handle 6 gpus