I found a refurbished 500 on ebay a few weeks ago for $130 and got it because it was more computer for roughly the same price as the 200. I hadn't planned on getting a cadence sensor, but after 3 weeks of riding with the computer, I decided to invest in one and I feel like it has really improved my riding. At the end of the day, I am really glad I spent the extra $20 dollars up front for the computer so I didn't have to replace the whole unit later down the road if/when I wanted to add more components.