Zenthar, to be honest, I didn't look at the motherboard choice at all, because as you mention, motherboards have little effect on performance. I generically suggested a P55 mobo, but didn't pay any attention to the one originally suggested. The best current value would be either an i5-750/750 with non-bargain-basement P55 mobo or an AMD Phenom II X4 955/965 with an 870 or 890 GX/FX mobo (depending on how much you want to spend).
OP, you should strongly consider filling out the info requested in the How to Ask for New Build Advice
thread to get a better recommendation for your budget.