I had one of my tube amps (a Roy Blankenship Princeton Reverb clone) modified to accept the monitor out signal from my KPA toaster, and the results are wonderful: amp-in-room tone with real 6v6's and a Gold Celestion 10.
One thing I would like would be to have an option to *mix* the cab into the output. Currently it's cab on or cab off. At the moment I prefer cab on, but I'd like to be able to dial the cab back a bit. It makes sense to me that this could be a simple *mix* control if nothing else. The ideal solution might be more of a *strength* of the cab sim control. This would all be in the output section of the Monitor output.