I'm new to PS Audio, though have been in hifi since the early 1980s. I've mainly been a Brit-Crit - done the Linn/Naim/Exposure/ProAc thing for a long time.
I recently got a pair of the M700 monoblocks - with all the stay-at-home orders, experimenting with the stereo was in order. While I obviously can't offer any definitive opinions, I can say that in my system, in my house, the M700s sound terrific. I *think* I prefer the Belles 350A Reference amp I bought at about the same time, but it's close overall, even if the amps sound different from each other.
To expand on the differences in sound, the M700s are airier and slightly brighter sounding than the Belles (note the slightly brighter aspect may be a function of break-in). The M700s also project a larger soundstage that goes beyond the outside edges of the speakers (Monitor Audio Gold GX300s). The Belles sounds a bit more substantial, or fleshed-out, if you prefer. For example, it's easier to hear Lyle Lovett as a complete person with the Belles than with the M700s. And the Belles seems to have more weight - more sustain on notes - while the M700s seem to define the leading edge of notes slightly better. Again, please note the caveat that the M700s aren't completely run-in.
Neither the M700s or the Belles have the feeling of inner drive or liveliness that my Exposure 28 had; on the other hand, both make the Exposure sound relatively band-limited even as the Exposure makes the others sound a bit slower.
With respect to build quality, I can only comment on the M700s, and I would say they are well-made without being overbuilt. I don't know how they will fare over the long haul, but from what I think I understand of how the amps operate I'd expect them to be consistent over time and reliable in operation.
In terms of service, PS Audio has been terrific - good communication both ways, prompt shipping, etc. And the PS Audio forum is a good one - to echo what others have said, it's great to see people from PS Audio actively and meaningfully participate.
So I'd say that if someone is in the market for something that PS Audio makes, it's well worth trying. It's been around a while as a company, is responsive to customers, and makes gear that seems to be both high quality and reliable. It's gear may not appeal to everyone, but that's OK - part of what makes this an interesting hobby!
