The ca minx system is stealth and has pretty good sound, from what I am told!
Set up #1: EMP e5ti, e5Ci, and EMP e5Bi surrounds, Outlaw LFM1 Plus sub, EMP 10i10i sub
Set up #2: Def Tech SM450, CLR2002, SLS Qline surrounds and Klipsch 12wD sub
Set up #3: Philharmonics- BMR in a 2.0 system, music only
I faced some of the same constraints but on a slightly lower budget, and I ended up going with the Polk TL350 set with 4 sats and a center. I paired that with a Klipsch rw12-d subwoofer. The receiver is a Denon AVR-1913.
The sub seems to be universally heralded around here as a great budget subwoofer.
Have you looked at something like the MilleniaOne by Paradigm. You could opt for the 5.0 and get a nice SVS sb-1000 sub.
A second on the SVS SB-1000. Your size room where space is limited is exactly what that sub was designed for. It'll definitely be better than anything else you can find with that footprint (size) for $500 or less. Next step up is the SVS SB12-NSD which would give you better SQ and a little more output than the SB-1000.
If you wanted to stay underneath $2000 for receiver, speakers, and sub, the Energy Veritas V-Minis are a good choice