i use one of this with my mark IV and G system
http://www.ebay.com/itm/NEW-RJM-Music-Technology-Mini-Amp-Gizmo-Add-MIDI-Capabilities-To-Your-Amp-/231684334566?hash=item35f17663e6:g:r7IAAOSw9r1V8nhm
you new to buy the proper cable for the mark IV
you should use a torpedo live (or a studio)...
this things sound great and had a headphone out
for example..
https://soundcloud.com/gcespedes/where-the-shadows-fall-demo-blackflow
the guitars were a mesa mark V and a 5150III, i use only my torpedo VB101 for cab simulation...
i always use mi...
is easy to replace the speaker in the combo?
i have a V30 and or an EMV12L in home that i think it work better than the C90.
but I don't know if is too dificult to replace the speaker...
greetings