I will. Right now the average American pays $10K/year. If there is any reduction at all in that number, then people can use some of that for add on or substitute policies.
Having said that, as I posted above, I am not at all convinced that the public single payer system alone would reduce the overall expenditure of $10K/year. Someone would need to convince me that the single payer system would reduce the 10K. The only way to do that is not through the insurance coverage, but through reducing the underlying costs of health care. In some senses, Congress is arguing about the wrong thing. More competition among providers should reduce costs. More transparency.
In any event, I would never support solely single payer. There would always need to be competition from private insurers. The money is out there, we just need to spend it more efficiently. The market is the answer.
Ooops. Edited to add link:
Here's how much the average American spends on health care