Which one depends on how much tweakability you need in the output (Studio @ $49 is the minimum!), and whether you need HD. The free one unfortunately doesn't encode, only decodes, so there'll be an expense here one way or another.
It just appears as a QuickTime export option, quite easy to use and the results are, well, passable I guess!
You seriously don't know ANYONE with Windows that would do this for you?
You would have the benefit (if the website allowed it) of doing WMA v10 Pro which comes in around the quality of PS-AAC about a year ago (before CT's last major quality jump). Which is still pretty OK quality considering the low bitrates.