I looked at the LSi9s on the Polk site. The recommended power is 20 to 200 watts. They're rated at 88 dB sensitivity. So 88 dB at one watt one mets. 20 watts would drive them to 101 dB at one watt, one meter. 40 would get them to 104 dB, almost the max for "reference>" In room SPL levels will differ some, but there's unlikely to be a need to have a 200 watt amp in a normal house sized room unless you routinely listen at very high levels at a significant distance from the speakers.
BTW, I'd take the 200 watt number to represent the max the speaker can take without heat-induced failure, and in general it's fair to assume that speakers are compressing (not getting as much louder as input voltage would call for) by half their max rated power, so if you NEED the volume 200 watts would provide, you also need different speakers to actually reproduce that full volume . . .