I have 803d and use an HSU 15" sub in the middle between them. Not the best position for max bass reinforcement (SPL wise), but excellent for center bass imaging.
I have also plugged the vents on the 803s (with foam balls)to really tighten up bass imaging and transients. I cross the HSU over at 50 Hz with the built in HSU crossover.
I have also plugged the vents on the 803s (with foam balls)to really tighten up bass imaging and transients. I cross the HSU over at 50 Hz with the built in HSU crossover.