I realize there are additional factors I can explore such as speaker positioning and room treatments, "The MOST overlooked component is the room; no system will sound any better than it's room will allow" - would appreciate tips used to improve here. An example here is with the LS9's and a big sub one can load up the room in a real hurry.
The LS-9's are capable of playing to a -3db of 20Hz in most rooms. And they will pound out the lower region much cleaner and with better control that a big heavy sub woofer. So don't limit the range where the LS-9's are great and hand that duty off to less capable drivers.
But you can use them both together to good effect. Both can load and overload the room. But if used properly you can have good bass with lots of slam while still minimizing room loads.
If you haven't already, try letting the LS-9's play full range. In other words, don't limit their low end. Then move that big sub to the back middle of the room and run it out of phase from the LS-9's. This will even out the room load and minimize the loading in the back of the room. It will reduce room boom while still re-enforcing the bottom end. You will need to start with your sub at a lowest possible setting too. If you can adjust it to 25Hz or 30Hz and down then start there.
You don't have a lot to work with regarding the rest of the room. Heavy drapes on the windows to the right will be good though.
