Take some time, tuning using the crossovers, sub level, and EQ so most of what you play sounds good then use the sublevel to adjust from there. I have a pioneer with a 16 band graphic and no specific bass/treble controls. I found once I took some time and set my EQ and filters right I rarely need to do anything with it other than tweak the sub level from time to time to suit different recordings.
And, to be particular, in my opinion you do have bass and treble controls. That would basically be a 2 band parametric EQ centered around a certain frequency in the lows and a different one in the highs. Now you just have more control over different frequency ranges in those categories.