One fitness machine for my house

[Bulldog]

I want to purchase one machine for my house, preferably $400 or less. I have a bench and some free weights already. I'm thinking a bike is the way to go, because right now between the two, I'd rather lose fat than build muscle. I have looked into Bowflex/Crossbow a little, and they seem like I would get some good use out of them, however. Thoughts?