is there a vaccine for upgradeitis? I can't imagine your system not sounding fantastic but yeah I understand the disease "What am I missing???" There is no cure but there is always ways to stave off the impulse to mortgage the kids and provide temporary relief.
Cleaning all the contacts could be all it needs to get that last ounce of nirvana.
Moving your speakers is also great pastime (don't forget the blue tape to return them back). I'd also try moving your sub to different places in the room, closer to the wall or pulled out more into the room, away / closer from the corner . As you've become attuned to the way your system sounds that original setup might not be optimal anymore.
If you really need to spend money a couple of acoustic panels leaned up against the wall at reflection points would give you some ideas what treatments could do and if like what they do.
The last option if all else fails is for me would be to add an additional sub (or two) to address the inevitable dead spots in the room.
It's the journey... remember it's not the destination but the journey