Am I detecting correctly that you are on the cusp of jumping in and buying a power meter? From what I can see, everyone says to take the plunge. A quick googling yielded the following:
https://forums.garmin.com/showthread.php?t=2417
I just bought a Polar Power Meter to use with my CS600x because it is by far one of the cheapest on the market. It's not installed yet but I'll keep you updated.