Supposed to be the best GPU block...
http://www.frozencpu.com/ex-blc-244.html
A really nice SLI setup, don't know of any other...
http://www.frozencpu.com/ex-blc-236.html
They are for 7800series, they make 6800 and may have to come out with a 7900 series. If you go dual ATI you may need to run separate GPU blocks with ramsinks???
1/2" tubing is the largest that is readily supported with CPU/GPU connections.
Here's all the pump you'll ever need
http://www.pondliner.com/PM5.htm