carvin legacy for solo's, triaxis for rhythmy crunch!
Actually, I've kinda pondered a similiar setup myself. Lately, I've opted out on amps, just 'cause the modeling units are so good nowadays, and it's really easy to go direct. Saves hassle, easier to tote. Sure, I know some are amp purists, and I respect that. After all, they set the standard. So, with that in mind, both sound like great choices. The Legacy excels for leads, with midrangey, buttery tone, it has a'plenty. But Mesa has some killer rythym crunch. How about a setup like this... (expensive, but if yer dreaming, dream big!)
1. Guitar into A/B/Y box...
*a. goes into triaxis preamp, into SimulClass 2:90 (or something similar) stereo power amp---
* *into right and left 2x12 or 4x12 cabs (spaced wide for stereo field), or a single 4x12 in stereo.
*b. goes into Legacy amp, placed center, for mono
*c. both outputs activated, for full surround sound! lol!
I'd bet it'd sound great, and you'd have a whompa killer system on your hands. Have fun!