I also recently purchased the Powercolor Radeon HD 7850 Eyefinity 6 for my company president's computer. He originally had a crappy LEnovo Thinkcenter, so we had to basically get him a new motherboard and PSU to be able to support the card. ( He had a mess of adapters before that would stop detecting some of the screens on an almost daily basis...)
Once we got the new computer built and setup, we automatically ran into issues getting the 6 screens to extend. At 1 point we get the screens to detect, but can only extend to 2 monitors at once. We installed the latest BIOS and chipset for the motherboard ( P8B75-M) and the driver for the card from the AMD site.
If you get any luck getting a 6 screen setup with this card please let me know, it would be very much appreciated.
UPDATE: We got this resolved! The issue was with the Display port to DVI adapter we were using. We ordered 4 extra adapters from star tech but they were DVI-Active, but we needed Passive. Once we plugged in the Passive adapters, eyefinity worked perfectly, hasn't given us a single problem since ( It's only been about 1 month)