It really depends whether you're trying to get your overdrive in the preamp or the power amp. If you're using an external power amp, with power amp modeling shut off in the Axe, you have to be loud enough to overdrive that external amp.
I bet the Rocktron is mostly preamp drive, so you should look for Axe presets that are also built that way. I'm not a super high gain guy, so I don't have real recommendations, but I bet lots of folks here can point you in that direction.
In that world, if you're getting comparable volume, then the power amp is getting a comparable signal level, and you don't need to worry about that part.
Hope that makes sense.