making a mustang snarl

Well, I have a new toy, a Fender Mustang I amp. I'll leave what I think about it overall on the amp thread in opinions once I've played with it a bit more. But I have a specific question for live sound: one thing I've noticed so far is that I can't get the same snarl out of it that my smaller Vox Pathfinder gets. The pathfinder is a straightforward solid state amp, not a modelling one, so it's possible it's just a limitation of the modelling amp, but can anyone suggest things to try?

By snarl I mean I can get an agressive fuzzy-buzz (a good buzz!) from the pathfinder on overdrive which sounds quite nice for classic rock stuff. It could be the smaller speaker, 6" rather than 8". I can get the Fender to growl, but not snarl so far.