Best treadmill mat to reduce noise/ vibration from a tread..

Hi,

I recently purchased my first treadmill and my downstairs neighbor
complained to me this morning about the noise (please reserve any
comments on my sanity for purchasing a treadmill when I live in an
upper-floor apartment -- the deed is done, and now I want to salvage
the situation). I know the obvious solution is to buy a high-quality
treadmill mat to see if that lessens the problem. My questions are:

1) What is the best treadmill mat to reduce treadmill noise and
vibration? Has anyone had a postitive/ negative experience with a
particular model?
2) Any other suggestions/ feedback/ ideas to reduce the noise?

Thanks so much!

Marci