Use B1 or B2 on the red and blue channels, bring up the mids and treble, adjust presence to taste, use excursion L on blue and excursion M on red. What kind of speakers do you use?
Another thing that you may want to consider is bypassing the mono/stereo switch in the back of your cab and in it's place install a single jack and use Marshall (different company) sound runner 10 awg wire to your speakers together, a la Bogner cab. I've a/b'd cabs that were done like this to cabs that weren't and it seems to make a BIG difference.
Keep in mind that my 101B is running KT88's instead of EL34's... here's my Blue/Red settings.
Excursion- M
Presence- 2:00
Treble- 1:00
Mids- 3:00
Bass- 11:00
Blue Gain-3:00
Red Gain- 1:00
Both on B2
The bigger bottles give me plenty of low end so I roll back on EQ settings. I also think that the XTC comes more to life with the presence up a bit. YMMV.