It seems that the Marantz only offer 80, 100, 120 for settings. It would seem that might be a problem. Is this a big disadvantage or is there ways around it?
Why is it a problem? The THX recommended crossover is 80hz. Of course it depends on your speakers and their low range frequencies which you have omitted to include, so we cannot identify your 'problem.'
I have a Marantz receiver hooked to four B&W 602's (low end of 49 hz) and LCR 6 (low end 60 hz) and the crossover setting of 80 hz seems ideal for music and movies.