i'm very happy with 1540 on air cooling atm...my board is a msi kt333 so i don't think i'll run it any harder till i water cool and upgrade my ram.
i tried being slick and went from 140 straight to 150 and when it rebooted my computer beeped insane and ;agkhaop[idhe'lakndsfl;kasd;lhte ran across the screen real fast filling it up, heh....i could probably get about 145 out of it.