Luxman, Marantz or Naim for Harbeth Compact 7

If you are somehow inescapably limited just  to your three listed integrated options: think NAIM

Upgraded superior option: LFD NCSE HR-II Integrated Amplifier

+1, I also feel the NAIM Super NAIT 3 amp is likely to be the best match with your Harbeth C7 speaker and subwoofer.  If possible, I suggest you audition the amp first before you purchase it   

Back when I had the 30.1 in the home office a few years ago, I tried them with Naim Supernait 3 and Luxman 590AXII. My money is on the Luxman. I found that while the Naim provided a more forward sound the Luxman had more depth and finesse. 

I have to agree with arafiq. I have the LUXMAN 550axii paired with 30.1 with rel s/812. The LUXMAN replaced a superuniti which was very good, but the LUXMAN took it to a different level. I never heard the supernait 3 but I suspect it has the same house sound as the superuniti. Akg_ca recommended the LFD which I know a lot of Naim owners switched to and swear by. Never heard the LFD but you might want to check them out.

I owned C-7’s for many years. While they do well with many amps they really shine with powerful solid state amps and love Class A warmth. Have you considered the Coda CSiB V1? Reach out if you want to learn more—I’d be happy to assist.

I have a Naim Super Nait 3 that sounds pretty good with Harbeth SuperHL5+. Similar listening tastes.

I’ve owned multiple Luxman amps (509X, MQ88uSE, M900u) and Naim (Atom, Nova, Supernait 3) AND Harbeth C7 (40th anniversary) and it really depends on the sound signature you prefer. The Luxman will be clean, powerful, detailed with a bit of sweetness on the top end. The Naim will be a bit less refined but more propulsive and will sound better across a wider variety of genres. 

Both amps pair excellently with the Harbeths. 

None of them. Accuphase.