i've been playing bf3 on bootcamp on my mac pro with a single 5870, and while i can play at an average ~60 fps on pretty decent graphics settings, i'm interested in getting the most i can out of this machine. i know the only gpu options for a 5,1 mac pro are either two 5770s or one 5870s... but i had an idea... i know these mac pros only have around a 1000w psu, but the 5870s not only run cool, but they also run very efficient compared to other cards, taking only about 27w at idle and 188w at full load. while the board on the mac pros only has two six prong power plugs for attaching a gpu, i figure i could use two six prong to two eight prong splitter cables to connect two 5870s in the mac pro. i only have a few questions for anyone that may wanna chime in: will that power going through only those two outputs fry the board or connections? while two 5870s would undoubtably work boot camped in windows, just like they would in any normal windows machine, what would happen if i left them crossfired and booted up into osx? would osx work normally as it does with a single card and just ignore the other card or would i get a black screen or whatever? if there's not enough power with the stock psu, would it be possible to switch out for say a 1200w psu to replace it? i know it'd make the inside of the mac pro a bit ugly and un-apple like, but would it be possible to bypass the six prong power connectors on the board and just run a power cable directly from the psu to the cards to avoid any board frying? what do you guys think?