Ronin,
I have the following Mission speakers connected to my Marantz 4300
Fronts : M73i
Center : M7C2
Surrounds : M71
SubW : Custom made w/ PP driver
Man, even this Marantz is a budget receiver, it can do wonders to the Missions specially after burning the speakers for 50 hours of music.
My set up is located with a lot of open space since the planned second floor of my house is not yet done. In HT it is great since the sound really envelopes you. BTW, speaker placement in my opinion is critical. While Iwas setting up the speakers, I have requested a cousin to move the speakers an inch at a time while I am positioned to the listening position.
If you are planning to get a Marantz - Mission Combo, try to listen to a 6300 paired with the M74i and tell us what is your opinion. This combination is like operation "shock & awe" (given the comparative cost with regards to other receiver-speaker combination)
Just my two cents.... I'm not an A/V guru and just speaking from experience.