You've well phrased the issues. While M22s are very good, in general M60s are well worth the upgrade. However your room is somewhat small. You have a great sub the STF-2. M22+STF-2 works very well (I used to have those). Re QS4 vs QS8, I haven't heard the QS4. But most of the sound in both movies and music comes from the center and mains, so in theory QS4s would be OK, especially for a smallish room.
Note the VP150 is fairly large and weighs 17lbs. Make your measurements carefully. If TV mounted, verify your TV will support the weight and size.
The system you first stated will sound very good. If you ever move to a larger place maybe consider M60s then. Just my opinion.
