Look at this review and you can see that the reviewer used a pair of Anthem Statement M1 monoblocks which are rated at 1000w.
http://www.soundstagehifi.com/index.php/equipment-reviews/557-kef-ls50-loudspeakers "
Then, for the heck of it, I tried the LS50s with the Copland CTA 506 ($6000), a tubed stereo amp that puts out 90Wpc into 16, 8, or 4 ohms; as well as a pair of Anthem Statement M1 monos ($3500 apiece), a proprietary class-D design capable of unbelievably high power (1000W into 8 ohms). The sound was slightly different with each amp, but one thing remained the same: the diminutive LS50s sounded much bigger than their size let on. I also learned that, with any of these amps, the LS50s could play
loud -- louder than I expected from speakers of their size, and louder than I really needed them to."
Unless you get really crazy stupid loud with your Parasound, I don't think it's 165w/channel will be a problem.
Bill