I think it would work. I was fiddling with a Vox AC30 the other day and did the same thing. I found a clean cound a liked, and stuck a distortion pedal in front of it and it wasn't bad at all. In fact I'd happily sell my Trace Elliot Speed Twin (Marshall on steroids), because the clean sound was so nice and the distorted sound was quite usable.

Notice I said that I used the distortion when the amp was clean; some amps don't respond well to pedals when already a bit overdriven and this was one of 'em. An overdrive pedal in front of it when already crunchy sounded bad to me.

Ya just gotta experiment.