"Wanted the A500 for older games that don't work with the A4000T."
IIRC, those old games could also be a problem for your planned 2.0x ROM upgrade. Introduction of 2.0x ROM is a giant leap in both GUI and optimization, compared with 1.3 ROM as former production ROM. Those benefits had sideffect of large fraction of game titles being unavailable without additional tampering (i.e. softkick).
AFAIK, Kickstart 1.3 (34.5) is the most compatible ROM for old games (OCS), with the exception of some very, very old games (pre-1986).
For that purpose, I would stick with 1.3
Take care
