If you haven't shopped for a new AVR in a while, then be warned that the mainstream brands are feature laden but sadly lacking in their power output sections. This is evidenced by their continued declining physical weight by using cheaper and smaller power supplies. One popular mainstream 7.1 unit weighs a whoppng 12 lbs! But it has all the bells and whistles.
IMO, there a two ways to go. Get the cheapest mainstream AVR you can (the popular brands change models every year so you can get last years model for 50% off this year) and couple it with a good multi-channel amp. This way the AVR is just a cost effective processor and it can be discarded every couple of years as the technology chnages but you have made only a minimum investment. This is what I do.
Or, if you truly want the AVR to drive a full a set of 5.1, 7.1, 7.2, etc speakers, look at the higher end brands like NAD, Cambridge Audio, Arcam, etc. You will be getting honest amp sections. If you want to stick with Japanese mainstream, them only look at the models at the top of their lineups. Then research them carefully to get critical reviews.
Finally, whatever route you go, make sure the AVR has a full set of PRE-OUTS so you can add a multi channel amp later. Most don't! Ten years ago, pre-outs were on most $500 AVR's on up. Now they are only found on $1000 models on up. Entry to mid level models that need this feature the most, do not have them. Hope this helps.