@cstrickland Sounds like you are trying to keep using the McIntosh mx113 as the preamp and only use the Kenwood as a straight power amp (i.e. bypass the preamp side), correct?
You might be able to feed the McIntosh's output into the Tape Rec loop, but you might over drive the Kenwood. Either way, you will be using both volume controls to control the signal. It could get ugly and damage the equipment.
Are you looking to use the radio tuner in the McIntosh? If now, why not just run everything through the Kenwood? Or just purchase a <$200 cheap amp on Audiogon/USAudioMart or even Amazon or eBay. Even an old Adcom GFA-535 ill probably sound better than the Kenwood.