Will I get cleaner sound with an XLS Crown amp going to the speakers though?
How many channels are you planning on running? If you are using all 9(?) channels of an AVR that is a radically different scenario than using 5 or even 7 channels!
The Crown would only be audibly cleaner if you are over loading the AVR amps and pushing them into clipping/distortion! Both the Crown and the AVR amps have very low (as in inaudible) levels of distortion if used within their design capabilities!
A Denon 3000 or 4000 series should do fine with such efficient speakers and if you will off load the lower frequencies to a sub, but I gather you might be using different speakers for surrounds.
Just get the AVR first, then see if you hear any distortion when you crank it. If you do, off loading 2 channels with a single Crown would make a significant difference in what the AVR can do with the remaining channels.