I'm seriously considering the Sigma Rox 10.0:
SIGMA ROX - Overview
does what I need (cadence, speed, GPS directions, power meter (when I can afford one), links to Strava ....
it does loads more, but at the moment I'm only interested in the above .... and it's very good value for money. I have been using the Sigma cheaper computer that has cadence, and it works flawlessly