Bass wise, on our backing tracks we have drums (midi created using NI Battery) and bass guitar (using one of the instruments in Logic pro).
Interestingly in the venue we play which their own system, we do not connect their sub because there is just too much bass and it over powers everything ( we have no control over the power amps, they are locked away, only the mixer and we tried eq'ing the bass out but no good with the sub connected).
We do get a great sound with adequate bass from the Martin audio speakers though so I figured the deep switch on the K12's might suffice. But the venue with their own system is quite a small pub, about 150 max so perhaps that's why, and for a larger club we would need at least one Ksub. The cost is an issue then though, unless you want to buy my Bose kit for £4.5k. (LOL)