I had the same issues using the Matrix into a real cab,
Hmm.
If that's the case then either you're not dialing in your tones very well or the Axe itself might just not be for you.
But it's probably the former rather than the latter because the Axe is known to sound as good as any real amp ever sounded when used in this configuration.
Unlike many folks here, I'm not all gung-ho about the Matrix power amps either.
[I own a GT1000 1U btw and just sent back a GT800.]
But they do do a serviceable job of translating the signal the Axe puts out and amplifying it in a musical way that sounds musical through a guitar cab.
They GT1000 isn't real pleasing for powering passive FRFR cabinets in my experience, but many folks here will disagree with that.
But if you get a chance to compare the way a Matrix power amp sounds like driving guitar cabs vs a hi-end power amp, like a Bryston, driving guitar cabs you'll readily hear the flaws in the Matrix's sound.
Contrary to what most folks here seem to believe, my feeling is that even the ART SLA power amps come closer to an uncolored tone than the Matrix amps.
But they pale next to a Bryston too.
As I recall, the QSC PLX Series power amps sounded pretty good.
They're light weight and powerful.
My issues with them were that they were 2U and I wanted 1U and the fans were a bit noisy for my purposes.
I suspect that the Carvin ss amps would sound real good with the Axe although I have no direct experience with them yet.
There isn't a tube driven power amp on the market that I am aware of of that will not color the Axe's signal.
Some people here seem to like coloring the Axe's tone in that way though.
IMO That's fine as long as you know that that's what's going on.
That Carvin tube power amp you're checking out is only 50 watts a side in stereo.
If you use one side only for a mono gig you'll probably find yourself driving it into clipping, especially with clean loud tones.
You might even like that sound.
But it's not the Axe making that sound, it's the power amp making that sound.
Even in stereo,with only 50 watts per side, on in mono bridged mode for 100 watts, you'll probably drive the Carvin into clipping if you have to play any loud clean stuff.
As for me I'd rather have all my tube-power amp breakup simulated and controlled by my Axe FX's Amp Block settings.
My power amp that amplifies the Axe is just supposed to make the Axe's signal louder w/o fucking with it in any appreciable way.
Even if you don't drive the Carvin into clipping, that amp will probably color the tone in some way.
But Carvin does claim that this amp, unlike most guitar-oriented tube power amps, can be operated w/o much or any coloring, so as far as tube power amps are concerned it's probably one of the ones that's more suitable for use with the Axe.
But for me, I prefer all the tube tone to come from the Axe itself.
That's what it's designed to do.
It's designed to get all of the tone of a tube amp into a FLAT ss system.
IMO Get the flattest, most audiophile power amp you can afford with at least 100 watts per side, preferably 200 watts or a bit more.
That's the only way to really know that you're hearing the true signal the Axe is producing.
But even if you do use a sub par power amp you can still get great tones out of the Axe-FX.
You'll just have to spend more time in the depths of the Advanced Amp Parameters tweaking things to compensate for the sonic artifacts that your power amp is imparting on the tone.
Those Advanced Parameters are pretty powerful.
With a really good power amp the default parameters of the various Amp Types all sound killer and all you have to tweak are the 1st page parameters: Gain, Tone, MV, etc.
Good luck.