Ive been gone for a while...sorry guys.
Atomic, to test the real power you are getting from your amp you need a clamp meter and a DMM. If you still want to know PM me.
Oden, You will want to wire them like this
Once you wire them like this you will want to bridge the amp to a 4ohm load and use this math.
sqrt(200*4)=28.28v
Erich, I agree the best way is an O-scope. I disagree with setting by ear. You might be able to hear clipping once its to a point that its audible, but clipping isnt always that way. It can be for a very short amount of time and just enough time to burn up a coil or lead...Gain setting with a DMM is the best method for a newer person for the only reason that music is recorded around 10db quieter then a true sine wave. Thus, the amp will never clip.
Fej, You are correct about the power of an amp. But in all reality most amps that are of decent value produce what they rate or more power. I have seen profile amps produce rated power on many occations. Thus even though you may not be getting the full potential...you are still getting exactly what you need.
As far as setting by ear...I wont ever do it for the simple reason that my speakers arent cheap and I sont want to replace them just in case. ;)