Rage19420 has done his cards with antac 620s in sli as a few others who have used the antac 620s.
and i think there a one or two more here
Ive done the H70 with a 560 and 580. The 560ti was super easy. Great oc even without a fan on the pcb and only cooling for the chip via the H70. Id still look for heatsinks for the vram but with my 580 i can monitor mem heat and its never been an issue. 68c max is like nothing for ram. Ive oc the snot out of my ram also and its still not an issue.
click on pic and it will bring you to my flickr page with more pics of the mods...pretty sure more than what is posted in my log. Also you can just ask and ill be able to respond to any specific questions you may have. My temps with the 560 were pretty low.... to guess id say in the lower 20s....23-24c range and NEVER went higher mid 40c for reg gaming and stuff.
Worked well, ask the others