I have 2 cards exactly the same except for one thing...memory on one is Hynix and memory on the other are sammy's. They are both XFX 8600 GT's but one is the xxx version being overclocked some. The one with the samsung is the overclocked. My question is should I flash the slower one? I plan on doing a SLI with these....what do you guys think? And which one should I make the "daddy"  card?

Der Meister

I'd flash the lesser one to get them the most up to date. That way you'll have less problems with SLI. as for who is #1 either will work