Hey don't get me wrong, I don't wanna burst your bubble, when this 300 worked it grew on me straight away, I've had a Spider Jam for a long time & have always wanted a Variax and the opportunity finally arose and I was not dissapointed with the modeling, the 12 string is awesome and to be able to change tunings at the flick of a switch is mind blowing, you can play whole tunes by yourself, as an example I made a patch that dropped the high and low E strings down to D then Virtually capoed the 2nd Fret giving me the tuning for the chain, I had a bass sound on the next switch and a Les Paul on the next, lots of fun, and with the ability to change the guitar setting with a stomp as well as the actual tone using my X3, which the Variax lead me to buy, So yes your Xt will power the 300 and with the digital Cable you will also be able to change the sounds, from having this 300 for such a short time I will definitely be buying a JTV. So go for it and good luck to ya ;)
Just to add, my 300 is now fixed yes, thanks to the help and support of the Line 6 techs I recieved and sucessfully installed a new piezo and boom, back in the game.