David, the proposed setup looks(and should sound)good. The mains are separated about as much as your distance from them, the surrounds would be just slightly behind your ears. The sound from the back mid-woofer of the QS wouldn't be "lost" in the kitchen, but would help create some back effect. 16ga should be fine for those wiring distances and may be easier to install and handle.
The location for a single sub in the left front corner is likely to be the best for a strong and smooth response. Dual subwoofers at the midpoint of the side walls should be even better, and although the exact midpoint can't be used, your proposed location below the QSs should be close enough to give a good result.
