Well since you just upgraded your LCR, my questions are. What kind of budget do you have, and is there upgrade time on the sb1000? Imo/Ime that’s much too big a room for a small sealed sub. Depending on listening habits a ported 15” would be the minimum I’d look for, and truthfully a pair would be a lot better. Especially since as an educated guess you’ll have a more sensitive system and will probably push it a little harder. The sb1000 will definitely be lost in the mix. Also, multiple subs should help even out the FR especially if you can take the time to set them up.