X48 vs P45 crossfire vs single card?

Alright my maximus X38 mobo recently fried itself, probably due to me putting to much force on the PCB when installing my water cooling setup. However i was recently considering buying the new Biostar I45 board. As many of you may know this board holds the worlds highest FSB record but im yet to find a good review on it. I was just about to order it when i saw a post that said P45 can only allocate 8x 8x to its pcie2.0 slots, i currently have an HD 4870 and have 2 choices either go crossfire or return my HD 4870 and get an HD 4870 X2 when it is released.

My concern is that if i go crossfire i will be severely bottle necking my cards on P45 as shown here: http://www.tweaktown.com/articles/1472/7/intel_p45_vs_x...

But i noticed on the Biostar I45 board that you have to switch around jumpers in order for crossfire to work, i know no matter what that dual HD 4870s will be bottle necked but im wondering that maybe biostar did this so that if the jumpers are in non-crossfire postion that the main PCIE2.0 slot would receive full 16x bandwidth. If this is true than if i got an HD 4870 X2 it wouldn't be bottle necked.

Im basing that just on a guess but im wondering if anyone knows if that's true? Will P45 be bottle necked on a single card? Because if each slot is 8x bandwidth no matter what than i cant see why even a single card wouldn't be bottle necked.