Combining 3 PCIe cards. 2 in 16X slots and 1 in an 8X slot

I wouldn't worry about it. The x16 or x8 refers to the number of pci lanes available which equates into available bandwidth for the slot. That card is not near fast enough to utilize the bandwidth a x8 slot provides, so there will be no difference between the x16 slots and the x8 slot.

Hello,

I have the same pretty much the same problem. I'm setting up a Stock Trading Station. I'll be using 6 monitors. My specs will be:

MSI 890FXA-GD70
AMD PhenomII 955
3x 4870 ATI Video Cards
6 monitors
1x Blu-Ray player
1x 200mm Fan
2x 140mm fans
1x 120mm fan
1x Fax modem card

Which of these will run this set up:
CORSAIR HX Series CMPSU-750HX 750W, single 60 amp rail
CORSAIR HX Series CMPSU-850HX 850W, single 70 amp rail

The 750 watt only has 4x Pcie cables, so I would have to use an adapter, not sure if that would be a good idea.

or will I need something with more Watts/Amps

Thanks in Advance

The 750 would have enough power, but since you would have to use the adapter I would recommend the 850. That is a very good power supply.

Thanks Andon48,
I was kinda leaning that way.
.