Finally I had time to properly test my card up to 1GHz+ on core.

Results are promising!

Stock volts (1.125V part) card will do up to 900MHz on anything (even Furemark!) but Crysis (less than 60s to crash)!
For Crysis V.High max. clock on stock voltage is 870MHz
Moving to 1.165V looks to make no difference ....
1.2V and welcome to 1GHz+ for anything but Crysis (this time it's bench stable, but not game stable - 15min+)!
1.225V and all is good even after 2h of cutting palm trees
1050MHz core not stable in Crysis (less than 3 minutes to crash).

What is good about those clocks is that all tests were done in closed computer case with GFX card fan left at Auto setting - working GPU temperature 80C-85C!

Loving this card so far!

PS. Memory is crappy on mine - 1270MHz max. stable on longer runs, 1300MHz for benching, but just!