You're going to need about 2 * 1200 watt gold PSUs for that beast imho. So that's at least $500 USD.
for 8 5770s? You're crazy. You don't need 2400 watts to power 8 5870s. A full system with CF 5770s was measured by anandtech as pulling 390W from the wall. Even ignoring the system overhead, 390W * 4 = 1560W. Many people have reported their AX1200s as being able to do that without too much fuss. Not a cheap PSU by any stretch of the imagination, but certainly not $500. More like $250.
Anyway, would the big bang marshal be capable of supporting all 8 of these? The main reason I'm so attracted to making an 8-GPU system is because is because repurposing it is an easy way to drive a 12-16 monitor video wall without messing with (the highly buggy) xdmx.
Again, you run the potential risk of burning out the mobo if you don't provide power bypass for some PCIE slots. They will also need to be single slot 5770s or else you will need to use extenders anyway. If they are not single slot you will need some sort of custom built rig to hold all the cards in place as well. Some things to consider.
Also I still don't have confirmation one way or another, but some users report issues with getting windows to recognize 5+ physical video cards. If you planned on linux anyway not as much an issue.