If you're not limited by the clock generator (which you will be if you use a multi 4 or something) then the lower multiplier possible SHOULD give you the highest speed possible. Of course, the difference should be less than the (MAXmulti - USEDmulti)MHz so it's not really worth the effort, if you ask me. You will almost never want to max out because that would mean you're on the edge of stability. I always bump down like 30-50MHz from my max stable overclock to avoid having any problems in the long run.