James, you are best not to put the MD600 in the listening room. It can sit on the network elsewhere.

If 808.3 is a stretch too far them MD/MS600 is the way I would go. Speaker to the dealers here and get a price. SQ from this into your 5k will be optimal.

I would say that 808.3 and 818 are only worth doing if you have more capable DSP's. And then I still think I'd go with the MS600.

Rgds,
Nick