Yes, I have a Luxman M-700u amp. For context’s sake, I rotate it with PS Audio M1200 mono amps and ModWright KWA99 mono amps. I use it with PS Audio BHK, Luxman m700u, DeHavilland UltraVerve III, and Modwright LS36.5 preamps. It’s used in two systems, one with Tidal Piano Cera and the other with KEF R7 Metas. Sources are either a Luxman D-08u or Auralic Altair G2.2 in the main system and an Auralic Altair G1.1 in the KEF system.
The pairing of the Luxman m700u with any of those preamps is always excellent but of course some suit me more than others depending on speakers. I will say the two Luxmans together tend towards an un-editorialized and straightforward sound with the Tidal speakers (which are extremely unforgiving of anything substandard.) That may sound like "damned by faint praise" but it’s not. I just mean in that context, the pairing passes the sound from source to speakers without doing anything to sweeten the sound. At present, I’m pairing the Luxman amp with the DeHavilland UltraVerve and it is a match made in heaven for my tastes. A prefect blend of resolution and musicality with the Tidals. It is also a very felicitous partner with the BHK preamp. The KEF speakers aren’t as resolving, so they’re happy with any combination of m700u and various preamps. The fit n finish is beyond reproach, exceeding anything else at their price point I’m aware of.
Regarding my opinion vs. published reviews: Audiorom.net has the most accurate commentary in my opinion. The reviewer says " ...the 700s to my ears were a bit more analytical than the Luxman 900s. Their sound is less saturated so it has more light in it. It spectrally prefers instrumental transients to fundamentals. The 900 combo was more organic, richer, and more complex. I believe the 700 combo should be a great partner where extra light is required, like some silk dome speakers that usually roll out pretty soon in the top octave." (I slightly edited for brevity and clarity.) His review definitely mirrors my own experience and opinion.
I certainly considered the Luxman 900 amp but it’s just too big and heavy. Now that I’m seventy years old, I have a self imposed weight limit for any gear and the m700u fits that requirement. I would buy the amp again without hesitation.