I currently have a PNY GeForce GTX 260 with 812MB of memory as my GPU, and am looking for a BIG upgrade. Does anybody have any suggestions of a good, ultra high-performance GPU for me, the price range doesn't matter as much.

My Criteria:
Substanitally more memory on-board
HMDI(mini is okay) output
Something really fast
Can be overclocked safely if needed
Nothing much else, just what works for you guys or you know works.