The basic point is that you don't need PRNAV to end up with an avionics fit where your autopilot can track a preloaded arrival track.
My old
KLN94 ($5k or so when new) can do all this, except it doesn't have the RNAV procedures whole in its database (it has the waypoints by name). An almost equally ancient
GNS430 does have them (
AFAIK) so that's you done and dusted.
No need for PRNAV.