After much research and consideration, Tom Thiel has settled on Clarity CSAs for the upgrade.I think the decision probably comes down to cost/performance ratio. If you were to do the upgrading yourself, I would highly recommend something like Mundorf Supreme or some of Jantzen high end caps.
He even has a custom low voltage version to replace the electrolytics.
My guess is the electrolytics caps are in the shunt signal path so it may not be critical. Also, they tend to be of very high value (like 50uf or 100uf higher). So it may be expensive to replace them with poly cap. For example, a 100uf Clarity CSA cap is about $100 dollars.