You might even get all pre delays @ 5, or maybe even 4, dependant on the ram. Write to pre dealy can go to 16 most likely, without affecting bandwidth too much...I'd run 16-5-1-5-5 myself.

PL @ low setting requires increase in chipset volts. 6 required 1.45-1.5 for me(dependant on whether I was running 2 or 4gb), 5 would not boot, 7 required 1.35. That's a big jump in volts from 7 to 6. If your ram will run CAS 4, 7 and 6 may be a bit easier, but I was running 400FSB/1066 mem @ PL6 24/7.