Ideas for used SS amp

I'm not sure I would use something as good a the Pass just for bass, not if you might be going full range in the future the Pass is one of the better choices for high-powered SS -- do you need that much power to drive the VR5?

The Carver zr1600 has variable gain to allow matching the Cary and can be bridged for massive power and shorter cables.

If you are looking to sell one of your amps I am assuming you are vertical bi-amping the pair. I am surprised that you find the bass lacking, but I have never heard your speakers. I have Alon V MKII bi-amped. the speakers are not overly efficient. I changed from bi-amped Sim Audio ss to the cary v12r and have been very happey with the switch. I would advise keeping the second v12 and auditioning a ss amp before making the final decision.