The Stealth doesn't have midi. The Blue Chanel is not the Same as the red. From what I've read, The Blue in the Stealth uses the first gain stage of the red channel, but is still not a 2nd red channel. The difference of the "normal" stealth and the EL34 Stealth is more than just the power tubes. As mentioned in other threads power tubes have almost no impact to the overall sound. To my ears both amps are voiced differently.Stealth adds a depth knob, two red channels and midi, otherwise it's the same. Easy to do in Axe.
I have tried to modify the 5153 in the Axe Fx to match my amps, haven't been able to though.
Haven't tried it with Cygnus yet. I'm really enjoying the 5153 50w in this FW.
I own both, and they are my favorite amps. I'm still hoping for the addition of those models to the Axe Fx.