I don't know who makes RCBS furnaces but mine:
1) Do NOT suffer spout freeze up like the two Lymans did (even after factory service/adjustment), and
2) Do NOT have to be run wide open. My thermostat dials are set between 700-750 and work fine for me.
My first preference would be a pair of original SAECO furnaces as made when Bob Modisett owned the company. Unfortunately that is not possible and Bob is no longer with us.
Good shooting and be safe.