It sounds like you play in the band and also run sound - if so, I'd work to make your setup as simple as possible. Ditch your analog mixer and get a digital one with parametric EQ - way easier to sculpt sounds, do real HPF filtering, and have room EQ set.
As for aux subs, I tried it for a while, but when running sound while playing, it's another thing to remember. Better to have just the channel fader to worry about and use digital EQ on your new board to HPF what doesn't need to be in the sub.
Less thinking, more playing. I even sold off the 5 Audix tom mics I had bought as I realized 2 OH mics (hi-hat, over the shoulder) was fine and less mixing for me to worry about, and it still sounded great.