I've had a K3 with a KRX3 for quite a while. I recently purchased a K3S. Can I put the KRX3 into a K3S, or must I use a KRX3A for a K3S? I upgraded the K3 to the new synthesizers several years ago, so if that's a constraint I already have the new synthesizer. Any other considerations that I'm missing? Dennis W1UE