Since you aren't going to have height channels, a used AVR sounds like the best deal for your situation. There are PLENTY of surplus AVRs around from people purchasing new models with Atmos and DTS:X support. I would suggest NOT focusing on any brand's cheapest AVR with pre-outs. I would recommend a mid-priced mid-range model AVR since it will have the same chips and analog circuitry as the top of the line AVRs while the cheapest AVR models will have cheaper components (often on the same circuit boards) that won't have the sound quality you probably want. You can even try the amps in the AVR. Around 2011 or 2012, AVRs had some kind of RADICAL change in the amplification circuits. Where EVERY AVR even Denon's $5000 model in the late 2000s sounded noticeably crappier than standalone amplifiers, after 2011 or 2012, at least the midrange models and top line models received new amplification circuits that sounded better than anything you'd been able to get in an AVR prior to that. You may find the amplifiers in, say, a 5 year old AVR sound so good with your speakers, that you don't even want to mess with an outboard amp. If you still decide to go the outboard amp route... aside from the big shake-up in better sound for AVRs in 2011 or 2012, amplifier sound quality evolves very slowly. You could use a used 3 channel amp from 5 or 10 years ago and for your purposes, it would be as good as a new 3-channel amp from a good company with modest prices. If you're not sure how to shop for used audio components, the safest place I know of that has a lot of stuff for sale is Audiogon.com -- this site supports individual hobbyists AND dealres. They have auctions and fixed price ads. They are clearly identified as whether they are dealer or individual ads. What brand of AVR... when every AVR got better sounding in 2011-2012, differences in sound quality between brands diminished significantly. As long as you stick to the main Asian brands and the few "step-up" brands like NAD (Canada) or Rotel (Japan) or Arcam (England) or Anthem (Canada) or Audio Control (USA, custom install dealers).
