For "audiophile level" receivers you may also want to consider brands such as ... Anthem, Cambridge Audio, McIntosh, Outlaw Audio. B&K, NAD, Rotel, Adcom ... and on and on
I would try to rig up a shelve that would be above the sub for the receiver to sit on. Maybe you could have it attached, hanging down, to the sloped ceiling in the closet
No one can say for sure but I would think Marantz fixed it they probably knew what the problem was (know issue) and they fixed it right. You may never have a problem again .... or it could die in a week. If it ever fails then worry about...
You've got me stumped. I did find this thread you could look at. ,,,,, http://www.avsforum.com/t/1016096/bi-wire-stereo-speakers-on-a-marantz-avr#post13570297 ,,,, Maybe someone there could help you.