Don't worry about balanced cables unless you need to connect the equipment in the way these were invented/intended- over long distance. There's no reason to use them unless the distance is great or if the equipment has no other type of connectors- the latter, BTW, doesn't guarantee that you can't have issues.
You shouldn't hear a difference between optical and digital coax unless McIntosh designed one to be better.
WRT the DACs- you'll have to be the judge of which is better. Don't sweat the cable quality if you try the digital coax output. Make sure it's decent, but don't fall into the trap of believing that cables need to be expensive.