Considering it's only 3dB spl for each doubling of power, if you're going to increase power go for a significant increase is what I'm saying. Speaker wattage max rating is generally easy to avoid problems with by simple use of the volume control....most speakers won't sound good at max level anyways. Now if there's someone in the house that simply likes to turn it up to 11....that could be another issue (you can always set your avr with a max volume limit too if you have potential for abuse). More headroom for peaks/transients would be another way to think about having more power, and an external amp would likely handle lower impedances better (the XLS are good for use at 2 ohm).
The XLS series is consumer friendly, has XLR, 1/4" as well as rca inputs. No audible fan noise issues I've ever had (nor most comments you'll find on these). They're not the prettiest things, tho the new gen 2 (the xx02 vs xx00 models) is a bit better looking I think. I've used them for quite a few years, both for mains as well as sub duties. Good value/performance. Do they have the lowest SINAD/THD? No but not an issue either. With really sensitive speakers you might get some amp hiss (with my 92dB speakers not at all an issue but I did chat with one guy with 109dB speakers and while he had no audio quality issues generally, he had a very quiet room and couldn't handle the hiss....he even had issues with a Marantz pre-pro IIRC with some noise issues, don't remember what he opted for....ended up going with the Benchmark amp I remember, tho).
ps Have you tried using an spl calculator to estimate your needs? Sorry about the size thing, the XLS are normal width but shallow if that helps....you could mount them away from your rack, too.
