I'm also cross shopping a few of these same models.
I think I've decided on a three channel amp for my LCR's, and just running my surrounds off of the receiver.
The Monolith looks interesting, especially as the current model now has balanced inputs. Being manufactured by ATI you know you are getting a quality product, but at the same time I wonder about the resale value down the line compared to brands with better reputations than Monoprice.
One thing that stands out to me though, is that the 7 Channel Monolith is an absolutely fantastic deal compared to the pricing of comparable Outlaw or Monoprice amps. The 3 channel model is $1,099, only $100 less than the 3 channel Emotiva XPA3 Gen 3, and the emo unit boasts much better specs.
That said, the Emotiva may be a bit much of an amp for my speakers. I wouldn't want my receiver (Denon AVR X3300W) to have to adjust the levels too far down. I'd imagine this could have SQ implications. Also, I ahve no idea at what level the Audyssey chirps play. It would be a bad day if my speakers (rated to tolerate up to 300W at 4ohm) would get a 575W @ 4ohm Audyssey chirp
Once set up, they ought to be fine though.
One thing I really like about the Monolith unit is that it is only 7" tall. This easily fits into my entertainment stand. The Emotiva unit is 8" tall, which would pose a problem.
I'm leaning towards the Monolith, but with that much more power in the Emotiva only $100 higher, it is very tempting...