I never heard any Emo amps and never like them, but apparently they have a lot of followers who also reported night and day difference of improvements simply by adding one of those amps to their AVRs. That just tells you how and why subjective reviews are not to be taken too seriously. By the way, so I guess you probably feel even the X4400H's internal amp could sound better than the XPA amp, to your ears anyway?
I think any decent power amp makes a difference. Over any reciever so I can understand why people have that night and day reaction. I understand that spec wise avrs running only 40 to 50 watts per channel on all channels driven can sound great. Especially in smaller rooms
But no one is going to convince me that giving pure undistorted power that can handle any impedance load or swing on all those channels driven especially to speakers that can handle lots of power even if they are efficient at 40 or 50 watts is not going to make a big difference in your surround sound or 2 channel listening experience. Id want that even in a smaller room just for headroom and dynamics without having to crank the volumes. The life it gives to your avr not having to stress itself driving everything is worth the investment alone
For example my denon X4400H which is known for running quiet hot doesn't even get warm since I've switched to all external amplification.
I am not bashing emotiva at all the amp didn't sound bad and to answer your question it still sounded better then the demons interior amps. Because the Denon can't keep up with it in pure power headroom impedance swings and dynamics with all its channels driven no avr can. It's just unrealistic. And I enjoyed a lot about the amp it's clarity dynamics and detail were all great.
But here comes the butt. I'm a big big stickler for airy laid back highs and midrangres. As much as you've noticed I'm a stickler for tight distortion free accurate bass. And the Emotivas had a bright forward presentation that I dont like that the crowns don't. They are just as accurate but the highs and midrange are laid back and mellow never harsh. I noticEd this with voices as well. Just a small and it could be in my head more natural presentation with the crowns and I'm big on voice presentation as well. But I don't think after switching back and forth it was all in my head.
So I'm not not bashing Emotiva at all for your money your getting a great product. I just like how the Crowns sounded better. But I would take the Emotivas all day over the amps in the Denon. Even if they have a better sound signature to my tastes. I'm never going to hear it because driving all channels to any level of usefulness there going to thin out and become bright and grating because it just can't keep up. Not in a room my size and that's not it's fault. No ave should be expected too. We just expect them too because companies inflate there specs.