I have the N584, which from what I read (I forgot to check when I had the heatsink off a few minutes ago) infinieon chips.
Vgpu and vmem mods are what I was planning on. have not even run the cards at stock yet... when my board gets back (should be here thurs or friday... (thanks OC!!) I will be putting it back under water and playing around with all the cards before I get to modding them
Just ordered enough pots for all of them... with a couple extra.
Going to look at quick disconnect stuff for water cooling, so I can water cool the 7600s in SLI and hte 7800s in SLI.. plus I have a WB for the 4890, I want to take for a spin....
Oh that might be a future mod too... OCP for the EAH4890

IIRC the leds on the back of the card signified OCP shutoff when I was having problems at 1100 core before. Dunno if keeping the VRMs cooler will help prevent that or not. The FC waterblock I got for it, guy included half an old socketA hestsink to drop on the block over the VRMs said it helped keep temps down