First congratulations again! In running, it is possible to run at a slower pace and have high cadence, you just take a high frequency of small steps, so your not running faster, just your turnover is high. A higher cadence over 30 minutes or an hour requires a certain amount of cardio fitness.

The best way to monitor an effort on a bike is with a power meter as you probably know already. I do not race, so paying $1000 USD's for one is not justifiable. If I was younger and raced, I would probably get one.