I've got the same amp as you,but with a different cab. (An Ashdown Klystron 4x10 4 Ohm version) I play a P and a Jazz,and my eq is like that (from left to right):
-Bass at 9:00 clock (but depending on the stage and room we're playing at)
-first slider in the upper quarter
-second slider at zero,or a little above
-middle at 12:00 or 1:00
-third slider at zero or one-two dots above
-fouth slider in the upper quarter,or simply at zero,depending on my mood,and if I play my P I like that fat not sizzly tone
-and treble at 1:00
Tube pre-ON and set at 2:00 or 2:30 to get that nasty tube overdrive.
Adjust the pre volume at 12:00 or wherever it needed to be. Sometime I switch off the tweeter in my cab,and just let the speakers give the top end. It's up to you.
With this setting I can get a really great fat growly jazz tone,and with little adjustments a thumping P sound. I noticed too,that the EQ switched off can get a really great old-school sound,with the tube cranked.
Hope this helped you in your quest of "searching the right tone"!
Cheers