From your detailed (thanks) advice on the adjustments, can I get some clarification on this part -
"As for the amp's crossover filters, I have the front SLC 210.25 NG (4"+1") hi-passed at 95 Hz, the rear SLC 230.25 NG (5.25"+1") hi-passed at 80 Hz, and the SWS-8X (8") lo-passed at 145 Hz. Nothing too scientific here, but it seems to work."
You are referring to the adjustments of the 3 channel outputs on the JL Audio right?
So switch to HP on Channel 1 and 2 and turn the dials to 95Hz and 80Hz respectively and LP for Channel 3 at 145Hz
BTW my front and rears are BSW and subs are SWS8s. Perhaps I should put both front and rear at 95Hz? I'd like a little more bass from the BSWs and I don't turn the volume up that much.