I’ve had a REF75 and a REF75SE for several years in my system and agree with all the points mentioned in the discussion, it is an excellent amp. It is a low maintenance model (for a tube-based amp) and it can drive many brands/models of speakers really well (I had Monitor Audio Platinum II which impedance curve can go low and it had no problem driving them). Obviously if your speakers have low sensitivity and you have a very large room, you may be disappointed if you want to crank it but many people who have listened to my system have been surprised of this was ’just a 75W amp’. Bass is strong and detailed but still ’rounder’ than with a SS like Bryston. But in term of sound refinement, it is much better than most options at this price point. Its replacement model is out so it’s possible to get the REF75SE for less money on used market and like someone said, a REF75 + KT150s give you 90% of the SE version for far less.
Synergy is important to get the most out of it (had paired it with a REF6 and the combo is great unsurprisingly). I’ve moved up the ladder since then but really enjoyed my time with this ARC combo and resell value is very high. Highly recommended.