I guessed, I didn't quite understand your setup. So, you are currently using the MF M3Si integrated amp for your front L&R speakers if I understand correctly?
I would certainly do that instead of using the Marantz amp to drive your front speakers as the MF M3Si is a better amp than any Marantz amp except if your have the Marantz Reference Series PM-10 integrated amp, that would be a different story. What Marantz amp are you using?

In regards to a monoblock amp to power your center speaker, dealers would usually sell a pair of monoblock amps but sometimes they will make an exception if you've had good and close relationship with them. What kind if speaker system do you currently have and if you're using an AV preamp processor etc etc?
Tell us about your setup and system in details otherwise we wouldn't be able to assist you any further.

markyboy156 wrote:

my marantz amp is 7010
i am usig a music fidelity m3i and a crown 1002
these are wired for the high and low frequencies of the dali ikon 6v2 fronts
the rest of my setup is dali zensor 7 rears dali zensor vokal centre 2 dali zensor 1 additional rears 4 dali c atmos upfiring speakers
4 svs pb13 ulra subs
using mini dsp 2x4 and antimode 8033
arcam ir dac and sony ux800 to enhance the music ability of the player
another arcam dac
and rega planar 3 turntable
playstation 4 pro
xbox one x project edition console
wii u
nvidia shield console
blue node 2 streamer

I don't want to be flippant or dismissive so don't misunderstand. I'm not sure how you can have a coherent sound with so many different brands of amplification. All solid state amps, held within certain distortion parameters will sound similar, but not the same. And there in lies the issue. Every amp you mentioned has different slew rates in the front end. Every amp you mentioned is going to have a different damping factor, which will make for differing distortion signatures in the peaks and valleys of speaker impedance. Etc, etc. Even the classic setup of using a SS amp on woofers and a single ended tube amp on top can be wrought with issues.

It seems like you'd have a much better and simpler and likely less expensive solution getting a very good home theater amp/preamp from Onkyo, Arcam or if it's your sound, Denon. Then IF you need more power choose a set of matching stereo amps, mono-blocks, or multi-channel that best drives your speakers. Fewer cables, fewer potential grounding issues, and you aren't chasing your tail and emptying your bank account looking for that "perfect" amp for just this one situation.

Just my opinion. Good luck.