oh ok.. im fairly new to modding pcs... so excuse my newbiness lol... The salesman at one of the pc stores i go to said x8 performance is basically half the performance you will get from a 16x.. so yea
No problem at all feel free to ask your questions.
x8 runs at half speed but it will give you roughly the same performance(in dual GPU mode),check this review http://www.tomshardware.com/reviews/crossfire-pci-expre...
This is a fairly old review but will give you the general idea about SLI/CF performance with different speeds.
Also,note that the gap becomes even shorter in PCI-E 2.0 cards/motherboards.
Unless you are running Multiple Monitors or one really huge one then x8/x8 is fine on a single monitor, where 'saturation' starts with x8 is when your resolution is very high: (1920 x2) x 1080 Dual = 3840 X 1080, or (1920 x3) x 1080 Triple = 5760 X 1080, or large 2560 X 1600 single monitors.
Yes, x16 is indeed twice as fast as x8. IF your plan is the run one of the above configurations then I would probably go either with an X58 with x16/x16; in particular 5760 X 1080.
Someone will argue the point, but I've seen the saturation data so post me some that contradict what I said i.e. prove it. Otherwise wait a few months for the 8-core X68; P67 are stuck at 4-cores.