Ram, that was the reason for my last two sentences above. No, the 23 models don't have pre-amplifier outputs for an external amplifier, but that may not be significant. As I said, a more powerful external amplifier doesn't necessarily give you "better performance". If the amplifier in the receiver has enough power for the sound level needed at your listening position, adding something that has even more available is meaningless.
The M80s are fairly easy to drive and use about 1 watt for a comfortably loud level at a typical listening position. Brief split-second peaks in the sound use much more of course, but the typical receiver rated anywhere around 100 watts maximum has enough headroom to handle these peaks at safe(to your hearing)sound levels.
If you studied the lab results on the predecessor model 2309, which I linked above for a different reason, you saw that the 4 ohm output measured was about 200 watts. If there're some other features of the 33 series that you really want, you should pay more to get it, but you shouldn't be overly concerned about power ratings.
