Optional chemicals for RA-4 that you may consider in addition to the Developer Replenisher RT #8415580 and Bleach-Fix and Replenisher #8309031
Kodak Ektacolor RA Developer Starter #1026681 to make 25 gallons
Kodak Ektacolor RA Bleach Fixer Additive #8036832 - 48 oz
I'm just getting started on color printing, having done it only once before years ago. I don't have personal experience with any of the RA-4 chemicals listed here yet, but I'll have a shipment arriving soon.
My understanding is that the Developer Starter creates a seasoned developer so that you don't go through the color shifts caused by aging of a developer that is mixed straight from the Developer Replenisher RT. The Bleach Fixer Additive provides added protection against oxidation of the bleach fix in a low-utilization system.
I just bought all four of the above from Pakor. Pakor only sells the Developer Replenisher RT #8415580 and Bleach-Fix and Replenisher #8309031 in case lots (4x10L each). Shipping cost from Pakor was high, but overall cost was lower than if I had bought an equivalent quantity from Adorama. Unless you are going to consume a lot of the developer and bleach fix, it may not be worth the savings to buy from Pakor vs Adorama. But that's just my opinion.