Do you really have to ask. Get a sub.
...and a TV.
You could do something like this:
http://forums.audioholics.com/forums...1&d=1178179946
That's actually a sub acting as a table sandwiched between the elliptical, the bike stand, and the bike rollers. The best part is I can listen to music or watch movies or TV while I work out too. Take my word for it, cheesy kung fu movies from the 70's are highly motivational workout material.