Hi dax,
I have an EP500 subwoofer on the ground floor of my apartment building (it was a factor that made the condo attractive when I purchased it) and I get no complaints. Deep bass in apt. buildings tends to bother neighbors below you and to either side (if you share common walls) rather than tenants above you. I run my system quite loud at times (peaks at 96 dB SPL) and my neighbors above have never complained.
There would be no difference in wall-mounted or stand-mounted QS8s in terms of sound transmission to neighboring apartments because the surrounds carry no deep bass, so it's the total acoustic output of your system that might bother neighbors if you run it too loud.
The only (slight) compromise in using QS8 Stands is the height. Ideally, the QS8s are at their optimum when placed a couple of feet or more above ear level when you are seated. However, they are very placement forgiving and I think you'll find that other forum owners of QS8s on stands report excellent surround envelopment.
Regards,
Alan
