Playing live, I run my 5150 head (lead channel) as follows:
Pregain - anywhere from 6.5 to 7
Post Gain - around 2.5 or 3
Low - exactly on 8
Mid - exactly on 2
High - exactly on 8
(the points on the knobs for the eq section make a perfectly horizontal line...)
Power amp controls, with a 5150 cabinet:
Resonance - 8
Presence - 8
If you don't have a closed back cabinet, or are using something equipped with Vintage 30's, the presence will probably split your head open. *The vintage 30's can handle that much resonance, but an open back cabinet (or combo) most likely can't.
For recording, where I double or quad-track quitars, I back the pre gain down a few notches and crank the post gain up to around 4 or 5. *Also when recording, I'm sure to engage the low cut filter on my board and back a little bit of the low EQ off on the channel strip. *If I don't do this, the 5150 eats the bass guitar right out of the mix.
Another note - now that I'm fooling around with Pod stuff, I've gotten the Soldano amp model to sound exactly like my 5150 head (w/o the hiss...) and I'm running it thru the effects return on the 5150.