I'm currently in the process of building a new machine but i'm stuck as to which M/B to get because of the RAM.

I am tossing up between the Gigabyte GA-M57SLI-S4 or GA-M59SLI-S5 because the S5 has Linkboost, which, if I have "Optimized for NVIDIA nForce" GFX and RAM then it will speed things up 25%. I have 2 gigabyte 8600GT GFX cards which means if I find the right RAM whamo.

Problem is I can't source any "Optimized for NVIDIA nForce" RAM so the S5 would have a wasted feature. So far i've seen that Corsair and OCZ advertise that they are optimised but I can't buy that through my sources, the S4 is $100 cheaper and doesn't seem to be any less than the S5 so...

Do I go S5 and try to source optimised RAM or save $$$ and go the S4 route??? If S5, where can I get optimised RAM at good price?