I really want a single channel that gives me the smooth to crunch rock sound.
I have the 50 watt HXDA, and I can say with complete confidence that it IS the smooth to crunch rock sound -
and much more. It's an amp that sounds great just about anywhere you set it up.
The Mesa is a great amp - I happen to be a fan of Mesa amps - but the HXDA is in a different league entirely.
First, just in terms of the most basic things, the HXDA is dead quiet at idle, unlike the Mesa, and unlike the early Marshalls. This very low noise floor means that notes don't have to overcome the usual "amp noise." Every detail of the plucked note jumps out, and the tail end of a note is not obscured by fading into noise, either. I believe this is often overlooked, but is one hallmark of a great amp design. It's especially wonderful for recording. If there's hum or buzz, it's coming from your pickups or your pedals or somewhere else in the system. It won't be the amp.
Whether this is the result of the HXDA's very careful hand-wiring or not, I can't say. But it is nice.
Second, there is a huge variety of tone on tap. The "HXDA gain" and the bass gain can be combined in infinite ways. The amp can be switched not just into HX or DA mode, the switches can be combined to your heart's content. I like mine mostly in DA/DA/HX, but with certain guitars, or for certain projects, I change it up as needed.
Third, it's a terrific pedal platform. If you like to use pedals to shape tone, get other sounds, etc., this is a wonderful amp.
Fourth, and most important, there are buttery tones. The harmonics in overdrive are rich and yet the sound is detailed. You hear your guitar, and you also hear the amp - this is hard to describe and probably harder to accomplish with most amps, but it's that holy grail thing where the guitar shines through AND the amp shines through, no matter how you dial it in.
As good as the Mesa is, there isn't that transparency.
Finally, the clean tones are
magnificent. If you set your guitar volume to 5 or below, the amp cleans up to shimmery, clear tones, and you can use the guitar volume (or the amp of course) to get as much or as little grit as you want. This is an amp that's designed to work with the guitar's controls, though, so be aware of that. If you're a guy who simply dimes the guitar, you won't get the most out of the amp.
So as much as I appreciate the coolness of the Mesa in many ways, the HXDA is a more interesting and more beautiful amp to play through - for me, YMMV and the usual disclaimers apply.