I've heard the Sonos stuff is great, so you definitely don't need the XL for that.
I am impressed with the TV functions, and despite having Sky+, I try to do it whatever I can through MCE. But then, this would work on any MCE PC, not just the XL- and bear in mind, the XL can only record one channel at a time, and altho is a hybrid, can't handle both analogue AND digital functions, so it's either or I'm afraid. But still, a decent MCE set-up would pee all over any 'dedicated' HDD/DVD recorder, just not necessarily the XL.
But the case, hmmm- it is one of the best 'front room' cases I've seen