gpu blocks, you cant go wrong with:
Swiftech, Koolance, Aqua Computers, Bitspower
In all honesty the difference is a meer few C's, and better VRM cooling.
That wont help you any in OCing, because overall general reductions on gpu cooling is usually HALF of what ur getting on air.
So get whatever u think is the blingest thats NOT EK.
And yea primochill was made for us from the getgo.
Tygon wasnt, it was made for something else we tried to adapt.
Tygon is heavy on plasticiser leach, and over time it gets disolved in your coolant.
Then your tubing starts to cloud, or you get that wierd waxy deposit on your res walls.
The thing about the 402X2 bay res is that u need that fix for it, or your gonna cry @ bleeding.
As for compressions, im very impartial to compressions... i prefer using silver plated barbs and clamps.