PowerColor Go Green 6750 (should be simliar to 5750).
875/300. stock voltage. 181mh/s (tried to OC to 925 and it crashed).
best thing is: it's fanless and only draws power from PCI-E interface (so no 6PIN power connector needed). Well, I have a case fan blowing it at it to keep the temp at around 64C.
I had the 5750 running at
exactly that earlier today, except it roars, and needs the 6pin. It entirely owns the 5450!