it all depends which Princeton it is. I have the Princeton II with the Riviera circuit and it can keep up with a Marshall Silver Jubilee pretty well. I also have anohter hot rodded one with 5881's that is way loud, and finally my Blackface is no slouch.
However the Princeton Chorus is a different animal. So overall, if it is a valve amp, I am not sure if anything transistor below 50 watts will do it, and in valve amps, a 30 might be more of a match than an outperformer.