and gain stages are simply how many triode sections of the tubes are utilized. basically, you can boil down most amps into tube boosters connected to each other, with eq'ing and volume adjustments in between. for a great clean sound, only one or two gain stages is needed (almost all fenders use 2) because the tone comes from eq'ing, and parts which inherintly cut or boost certain frequencies (speakers, tubes, etc.).
But for high gain sounds, you want multiple gain stages. Basically, when a tube is pushed into distortion, it compresses, and then clips. if you're getting too much clipping in the preamp, it'll sound like ####. Thats exactly why my crate v8 (2 gain stages) sounds horrible at high gain (check out my youtube channel for the awfulness). And thats why amp makers like mesa boogie use a ####load of preamp tubes for high gain sounds. plenty of mesas have over 6 gain stages.
anyway, yea, see if he used all 4. Also, ask if the master volume is after the phase inverter or no (post-inverter = more dirt). if he did those two things, its a sign that he knows what hes doing. then again, sometimes fender doesnt even do those things...
