512KB of RAM on a sidecar and jrIDE? jrIDE should have the 512KB that you need already.
Or do you have a different IDE solution?
I'd be careful with the power supplies. Three sidecars was a good rule of thumb. Some machines only have the 33 watt card, while others have the 45 watt card. And some sidecars like the Cluster sidecar should *never* be used without a power sidecar in front of them.
Mike