I read what your saying about integrated, but I would suggest something like the Anthem integrated with their room correction that will integrated your sub much better then what your proposing. Or their similarly outfitted pre-amp with room correction. there are many other similar pre amp - integrated with built in room correction that would serve you better in a 2.1 system then trying to chain together a preamp- AV pre processor- amps. Lyngdorf TDIA-2170 is another many are raving about. Micro mega m100-150 as well.
These also have digital ins and tuners so your not losing anything but gaining much better control of your 2.1 system IMO.
oh your Marantz in an integrated with av processing that you don't really need in a 2.1 channel system. Why pay for stuff your not using