The issue with the XLS, or mono-blocks for that matter, is outlets. I got five channels.
More voltage in gets them to their stated specs at a lower gain no matter what. This results in a cleaner sound at any given dB level with a steady hand.
I have been teetering on the edge with mine for years. Always shut down the right front when pushed on up there. Gonna get more balls this time around. I think the spec for my Adcom at 4ohm was around 180w, but gonna need more to prevent this from happening again.
You don't need as much power for surround channels as for the front channels. IMO, you could use a 2 channel pro amp for the front left and right channels. An AV receiver could handle the other channels. Should you need additional power for the center channel, you could purchase a second 2 channel amp. Another option would be to get a Monolith 5 channel 200 watt/ch amp, but that may not be powerful enough to your liking.
I suggest that you check this link first:
http://myhometheater.homestead.com/splcalculator.html
You want a good power amp. I would suggest the QSC DCA 1622. It's a 2 channel pro amp with a 300 watt/ch power rating at 8 ohms and 500 watt/ch at 4 ohms and it will handle impedances dipping down to 2 ohms without a hitch. It's one of the QSC's digital cinema amps used in Cineplex theaters across North America. It's retailed at over US$1100, but an online store in California, Socalcinetech sells it , I believe, at 20% discount. In addition, you can verify on QSC's website to find a local distributor. These amps are not carried by pro audio shops and are sold uniquely by cinema equipment suppliers.
I am using four of the DCA Series amps in my HT and these amps have amazing specs. They are reliable and you cannot blow them up. They are as acoustically transparent as any audiophile amp on the market. IMO, anything costing more than this is a waste of money. Put the saved money on better speakers if necessary, you would get more noticeable improved performance:
https://www.qsc.com/cinema/products/power-amplifiers/dca-series/dca-1622/
My HT:
https://forums.audioholics.com/forums/threads/my-7-channel-system.111234/