Spread spectrum is better left off unless you have emi coming from your computer affecting other electronics. It can cause instability when overclocking so I always leave it off. I couldn't unlock my 720 either so I don't think it has anything to do with that. I can't give you lower numbers each cpu is different, but don't be afraid to lower them and test. With my 720 I could hit 3.6ghz with 1.472v cpu vdd / 1.362v cpu-nb vdd / nb v 1.28 / ht v 1.22 / htt & nb at 2600 mhz.