Have you tried the AVR with any other speakers to make sure it is working properly?
You said it was your dad's old AVR, so I am wondering that there might be something off about it.
Also check the manual and if there is a "reset" option, I would reset it just to make sure there are not any errant settings lurking! If not, put it in "Stereo Direct" mode
Also make sure that (assuming you are feeding it from the TV) you go through the TV menu and disable any "audio enhancement" "features". The idea is to get everything back to the "plain-Jane" signal, then you can play with any tweaking from there. For example, a EQ system to help the TV speakers may artificially add bass and treble to help out, but with good speakers like the Infinity R162's you don't want that.
Is your source the TV? How is it connected to the AVR?
As you describe it, I think the issue is something bigger than position of your speakers. These speakers with the R12 should far exceed a Vizio soundbar (although I do believe Vizio makes some decent soundbars - but they are limited to typically 3" drivers and often the sub is more woofer than subwoofer!