Odd. I don't have an r520 to test this on obviously
but this is what mine defaults to.
It's a fresh install of HL2 as well so no tweaks there.
I have no idea why Ratchet said what he did. Maybe it is something to do with the r520's and their beta drivers? I have no idea.
Wrt IQ, I have personally not noticed any differences whatsoever between my current card and my old ultra OC. Speed is different but thats about it.