Yes you can. You will use the L+R front preouts from the receiver to the monoblocks.
Sure you can do that. I prefer to have my front soundstage(L-C-R) with the same amplification and let my receiver power the surrounds. With your configuration, you have the left and right channels at 200w and your center and surrounds at no more than about 120w each. I know wattage doesn't mean everything, but having a seamless transition in the front soundstage is very important to most. Why not try (3) MA-700's L-C-R and have receiver handle surrounds.
I would think the Energy rc 70 would do fine with the Marantz SR 6003. According to the specs. which are not the most comprehensive, it looks like it doesnt take a whole lot of power to drive the Energy speakers. You never know however, till you get there.