I have an older Panasonic TC P50ST30 (release review/specs here) that was generously given to be by another Arsian that does have ARC support (I think). The TV sitting in front of an old but nicer ...

Depends on what you are connecting to on each side of the converter and what you want to put through it (what type of audio content) and the resulting experience you want to get. In other words, ...