Yep, what the others have said.
(1) Get the guitar/keys to quit boosting their bass. Tell them THEY are getting lost in the mix and their solos will cut through SO MUCH BETTER if they concentrate on the higher frequencies!


(2) Boost the mids of your rig. The bass will be heard best if it sits ABOVE the kick drum. 400 Hz is a good range to start. Does that Ampeg have the typical "1, 2, 3, 4, 5" midrange selector switch? I have had good results on Ampegs by setting it to "2" (about 450 Hz) and boosting the level knob to about 2:00.
EDIT: I just checked the SVT VR manual - you have a "1, 2, 3" midrange switch where "1" centers at 220 Hz and "2" centers at 800 Hz. YIKES! The EQ selections on that amp won't exactly get you where you need to be. I guess you'll have to try setting it to "1" and boosting it, then try setting it to "2" and boosting it, and judge for yourself which one works better. And in the meantime, put a lot of effort into point (1) above!