1. I would never buy refurbished.
2. IMO going with separates (I have CX-A5100 and MX-A5000) is NOT about getting better sound quality over something like a RX-3070, which I think will sound just as good. It's about pride of ownership, which is personal.
I would use AVRs for all other rooms, but I must have separates (pre-pro + amps) in my main system for my personal satisfaction.
One other debatable factor is that separates might have better reliability than AVR. That's my 2nd reason. That's what I tell myself.
So if your ONLY intension is for sound quality, I would just stick with your RX-A3070.