I'm not sure why they told you this. Maybe they were thinking of the fact that a 9 channel unit like the Yamaha puts out a drastically lower amount of power in watts if all channels are operating .... but, as I understand your post, you are only using 2 channels. Right? Yamaha claims that if you are only running 2 channels it puts out a full 140 watts, 20 to 20 K, 8 ohms, at 0.06% THD. That should be more than enough, unless you are playing your music so loudly that you are into clipping ... not likely.
While all Klipsch speakers are very sensitive (require very few watts), the Reference series (or some of them) have the reputation of being "hard to drive" for other (impedance/current reasons). I'm not sure this applies to the RF7-II.
Even if you got a 250 wpc amp, that is less than twice the power, therefore less than 3 dB more output (doubling or halving the power results in a 3 dB change).
It is disconcerting when a respected manufacturer says something we can't find a reason for ... did they give you a reason, or comment at length?
The guy I talked to, at Klipsch, told me that he thought they were under powered. He said that at loud levels the lack of power causes distortion and that he feels this is what caused the tweeter to blow.
He recomended that I get at least a 250 wpc rms amp because that is what the speaker is rated for. To be honest, one of the BIG reasons I bought the RF-7II's is because they are so efficient, and a lot of people told me
that the receiver I bought would be plenty. I don't want to spend more money for amps, but I don't want to damage my speakers either.