I use puzzle mats that I purchased from greatmats.com. They're a bit thicker than the ones you might find at Target, Walmart, Sam's Club, etc. I have them over concrete and have found them to work well for me, even with impact cardio, and even with my 42-year-old knees. The mats were also more economical for me, as I could not afford to put in a subfloor and the laminate-type spring flooring on top. Maybe someday!
Good luck with your flooring!
Deborah