You can still find new RIAs for ~$400, so I would not pay $450 for a used one.
I had a Charles Daly (same pistol as the Armscor or the RIA) and I had a bad experience with mone. YMMV.
Given your choices, I might go with the Para, although others would go with the Springer. My GF has the Springer GI and the trigger is horrible, at least in comparison to any of my Kimber (all were bought used, several for $575-700).