KK,
I'll try to make this as simple as I understand it...
Sandy bridge as a FIXED base clock...you CANNOT touch it, because the memory controller (now on the CPU, like the AMDs) uses that clock...the graphics core on Sandy also uses the BCLK as a reference...they call in a "RING BUS"...so the non-K models can't be OCed more than a few mhz extra...you NEED a K-series (2500K or 2600K)
To overclock, the Sandy Bridge K-SERIES are like the AMD BLACK EDITION CPUs...the multiplier is unlocked...so as you cannot paly with CLK on SB, you raise the multi...
For the RAM, you don't NEED to buy RAM that can stand higher speeds (overclocking RAM) for Sandy bridge, cause teh FSB/BCLK is not invloved in the OC...
You can buy faster RAM, like DDR3-1600, DDR3-1866 or even more and get some benefits...you an also buy RAM that has "tighter timings" such as CAS8 or CAS7 instead of CAS9...
But if you look at this article
the-best-memory-for-sandybridge (BIT-tECH)....sorry can't cut/paste in firefox..annoying...
CAS9 1333 RAM is cheaper and perfect for gaming...it has a 2-3% lower performance compared to DDR3-1600...on the SANDYBRIDGE platform...
In my situation, I set a budget, and put more money on the motherboard and cooler quality, plus better fans, instead of spending $40 extra $$ for 3 fps...personal choice I guess...I added $500-worth of graphics cards...that more than enough to offset the loss of 3 fps on the ram....