Which Computer: Polar or Garmin?
 

I have been looking for a new computer and have narrowed it down to the Polar CS600 and the Garmin 705. I definitely want the ability to upgrade to power in the near future, but don't necessarily need that right now.

The Polar CS600 is a great device, but I would not recomend it for you since you said you were interested in adding power in the near future. The Polar power device may be a good option for some people, but in my experience it just is not very reliable. I had to send mine back twice. I had no confidence it would last much longer than the warranty so I got rid of it and bought a Powertap. It has worked great from day one. The 2009 Wireless Powertaps will work with the Garmin 705, so that seems to be the way to go for you.