If you're listening at levels that may cause clipping then 200 wpc is a good idea. It's better to have more than you need. I'm a firm believer in having more than I need and at present my 200wpc amp is adequate. I often listen at levels with peaks hitting mid 90's at my listening position which is about 10 feet from the speakers. The speakers sensitivity is 90db at one watt. You can easily draw 200wpc listening at loud levels when the bass is strong. More drivers are blown by not enough power is another reason.
200 to 300 wpc amp revised question
i forgot to mention in my previous question that the reason for leaving the threshold s200 at 100 wpc is that I purchased von schweikerts vr4. although i haven't even hooked them up to the threshold yet, i was told they would need 200wpc, actually in an email from von schweikert himself.