I have the Monitor Audio A100, and have the optical audio from my TV plugged into the amp. I love it!
I cannot comment on your choice of speakers, and also do not have personal experience with the other amps to comment.
The A100 has been a delight ever since I first heard it play. I sparkles with detail, has plenty of headroom, and creates a believable soundstage. On the downside, it is not a high powered amp, although it has plenty of power for music most of the time, and more than enough for TV.
I initially connected the A100 to a couple of Mission bookshelf speakers on stands. I was happy with the sound, but wanted more bass. I picked up a pair of MA Bronze 4 floorstanders, ending up plugging the rear ports, and am so far pretty happy with them. Although I mostly use them for music, the sound from the TV is terrific. In fact, and I could hardly call this a downside although it is a little unsettling, often sounds from the TV seem a little too real. Not explosions or knocks on the door, but subtle sounds that make me glance to the kitchen or outdoors.
I like the size and appearance of the amp. I have read that some struggle with the speaker terminals in back. I have 12 gauge bare wire, and had no difficulty connecting it, although I did take the amp in my lap and took my time to do a good job making the connections. There are a few other imperfections in the design, although I suspect every product is imperfect; I came recently across this article in which I thought the writer did a pretty decent job highlighting the its strengths and shortcomings. It's on hifi chouce (I do not have enough posts to put the link).
All that said, I would expect that you would have a good experience with the NAD or Marantz as well. The sound from my A100 is a huge leap from the NAD 7100 it replaced, but other changes were made at the same time, such as removing the DAC and wireless components, so I cannot isolate the changes to just the NAD 7100. The initial setup was a *****, although others report it going smoothly; updating the firmware made all the difference for me. Good luck and if you choose the A100 I would be really interested to collect your impressions on speaker matching!