Well not necessarily the most RMS is the best. I doubt you will be playing your music at full blast all day all the time, with the amp at full power all the time and if so it probably isnt going to sound the best after a while. and Your amp probably couldnt take it even if it was a great amp. But 600 is pretty good id say not a terribly high amount but should get plenty loud.
but what youre also having to look at is the output per channel. THose JL audio speakers it says have a max RMS power handling of 60w, and the Polks it says 180 but it never says RMS so im assuming thats max output not RMS which is constant.
I dont know anything about Cadence amplifiers, unfortunately, but i would be very cautious about hooking one up to such nice speakers. It VERY WELL may be a fine amp, ive found a few good reviews about it. But its hard to be sure, with it being a more unknown name. I would say it would be like going out and buying a really nice ronix or LF board and then getting ebay boots?
I would recommend something like this, solid company, good reviews, probably outlast the cadence, and 60w rms which is your JL's max RMS output.
plus its prime if you have a prime account
But end the end only you can decide if you want that amp or this one or any other one, im sure the other is a good amp. But its also worth something that with this amp you can deal with amazon if its shotty or malfunctioning, where as the other you deal with the seller
Hope this helps a little!