I used my laptop a few times, I used this setup:
Guitar--interface--tube screamer plugin--tseX30--that signal went to two tracks--one with impulses loaded in lecab
--one without impulses
the signal with the impulses went from output one of the interface to the mixer, the signal from track 2 without impulses
went into the fx return of the head that was standing there, so I was just using the power section of the amp into the
cab, worked out pretty well and was easy to setup.