I built (not for me) 4xTITANs on Asus Rampage IV Black Edition - fits all 4 Titans but as I wrote here
http://render.otoy.com/forum/viewtopic. ... on#p169922
there are problems with connection chassis cables under the 4th card - this is the problem for all boards unless you have low plastic chassis connectors.
I also bought Asus p8z77ws with integrated graphics - I returned it back. My both monitors went black after booting the system and many users on different fora reported such problem with z77 chipset. So avoid this board. After this board I am sure I would avoid integrated graphics.
My personal recommendation - go with Gigabyte - it is rock solid and
http://www.gigabyte.us/products/product ... id=4766#ov
is all you need - there is no need to spend twice for Asus WS or Rampage IV. I still have gigabyte UD4 and unless I need more PCI slots I am not getting rid of it.
If your GPUs are to be stock air cooled you'll reach temp. limit (about 80-84C) fast and they will be clocked at stock 836MHz core. The lowest coolest card will be about 70C and may run faster. So if aircooled - get yourself big well ventilated chassis. My personal recommendation - go with watercooling. All gpus will run at 45C and will be silent and you can use their 100% power or even more. My single watercooled titan is about 25% faster when overclocked on save 1.2 volts and 45C. 4x780Ti on water = 5x780Ti on air. All you need is a pump, 2x 4x120 radiator, waterblocks and reservoir. If you can afford it get it.
Shortly speaking - my recommendations are - go with gigabyte and water cooling (+ case labs chassis which is my dream, like the new mercury s8
http://www.caselabs-store.com/mercury-s8/ )
PSU 1500W.