We don't even need to pay down the debt, as long as we can keep the economy humming along and growing, and get spending under control, we are already reducing the Debt-to-GDP ratio every moment of the day. If we are able to reduce spending then we should be able to reduce the amount of revenue collected, causing the economy to grow even faster, and the ratio to continue to fall.
Interesting information on the debt here, read down a few articles, there is a lot of good stuff here:
Skeptical Optimist