Budget friendly receiver choice

soix, that one is near by (pawnshop) and I already offered them (but reduced their price since the needed software/mic is not included). Unclear if it handles my 4k TV (Visio M75). 

12many: last year may not be enough. Looking also at Marantz SR7008, a cheap SR7002 ($150), and some others. I need to make a list of SUITABLE receiver that come close to my wishlist, but then still need to research how those amps hold up under difficult loads, if they allow bi amping (using the 'spare' unused amps), have full 'pre out' (to use external amps for example for front/main speakers for 2 channel audio setup), if and what DSP they use, 4k capable, etc. 

Erik_squires: what does 'use audio return channel' mean? TV with that 'special' HDMI ? What is the difference between say 520 and 710?

Any letters with that Denon 4300? HDMI 2.1? Pre out? Bi amp option? Decent current (i.e. power in low impedance speekers)?

anotherbox, how did you 'manage' bi amping (what connections used) with the Onkyo TX NR6100? Looks fairly 'meager' connections (used to seeing 7 pre outs): 

The Anthem MRX 710 slipped through my hands. 

I scored an Onkyo TX-RZ81, which seemed to fit my wish list. Have not hooked it up yet. Has bi amping (zone 2 amps used, selectable in menu), should have decent power (not sure how it handles low impedance), has 4k pass through. Pre out for all channels. 

That goes with every purchase of a used item; can't have it both ways. And did not need (still not sure what is actually would do for me) HDMI 2.1. Or 8k for that matter (I still watch 95% in non 4k, so have likely a few years to even 'fill' the 4k that my TV has (and also my new old Onkyo) until the material I am watching has caught up. By that time, the next 'now $2,000' receiver is available for $600. 

Currently have an Onkyo; surprised to hear that Onkyo (particularly older ones) would be worse than the other major brands (Yamaha, Sony, Denon, Pioneer, etc). 

There is always a risk. But compared to for example cars (where its not just age, but 'owner treatment' and 'environment' that has a BIG impact on how they 'mature'), it a small risk. 

Found some actual output test results for my Onkyo TX-RZ810; 2 channels driven (still looking for multichannel numbers to better reflect bi amping).

Source:

Bought (used, with manuals, remote, dust cover, but NOT THE MICROPHONE) Onkyo TX-RX810. Just hooked up cd player (optical) and computer (25ft usb-c to Shiit, RCA to Onkyo). Just tried on CD (ripped losless) from player and computer, medium level. VERY impressed with the sound (computer actually sounded BETTER than the CD player (low grade Panasonic DVD player). Reading the manual right now, and will do some more listening, but impressed so far. 

No. 2 Channel Audio, 5.1 channel video, and trying SACD 5.1 Audio.

Soix: yes, 2.1 Audio, 5.1 Audio, and looking to buy (3rd attempt, 2 first players I bought were NOT able to play SACD; need palyer that offers SACD over HDMI, have a list of Sony players, need to find a cheap one). 

First impression (2 channel audio, played from cheap CD player via optical and same CD played from computer via 30 ft USB C cable to Shiit DAC, then cheap RCA to receiver) was very impressive (the Shiit combination was NOTICEABLY better, assume the Panasonic CD player is NO GOOD). 

I think that goes for anything 'mid level'. It is useless to 'qualify'  mid vs high xxxx in any field, wether it is a $250,000 turntable or a $2.5 Mio car (but the factor is 1000 for the turntable (vs mid xxx) and only 100 ($25,000 for a 'mid car'). Neither can be logically justified.