Hi moorejh,
The Marantz A/V receivers will generally not drive the 4-ohm M80ti's without current limiting (very limited power output). The A/V receiver brands that will drive them without difficulty in moderately large rooms (4,000 cu. ft) include Denon, H/K, and NAD. If very high sound levels are required in bigger spaces, we recommend at least a separate power amp for the main left and right channels (the M80ti's) capable of high power into 4-ohm loads.
If huge spaces and very high SPLs aren't a requirement, the M60ti's are an easy 8-ohm load that your Marantz would drive. Tonally, almost identical to the M80s, with only slightly less peak output and deep bass capability.
Paradigm are decent speakers, but the M80ti, M60ti etc. are generally more neutral and accurate than the Monitor series. The Axioms are comparable to the Reference Studio models (I think the Axioms are a tad more neutral). Paradigms tend to have a 3-dB or so hump in the upper bass that gives them a bit of a fat, "bloated" sound on male vocals, etc.
Regards,
