Improved the speaker system today with a nice AC/DC amplifier and it's loud... really loud. Finally I can wake the neighbors with my machine!
I've moved the amplifier from the cabinet to the head, and I've put the audio controls (tone, volume, power, headphones) on the back of the head. I don't want the controls to be sticking out from the head so this will be covered by a steel grill later on, so it won't be that easy to adjust, but still possible.
I've also plugged in the nice Stern 8-Ohm speakers and resoldered the passive mixer with thicker cables.
Basically I will be putting the display, speakers, amplifier and everything related to that inside the head and the rest of the hardware inside the cabinet. The head will of course be connected to, and receive its power from, the cabinet itself.
To sub, or not to sub.... that's the question.