I ordered a Quarq power meter today. My 2009 CAAD9 is currently set up with a Garmin 705 head unit which has the cadence unit on the chainstay. My question is, do I leave that unit on my chainstay, or with the Quarq don't I need it anymore? I guess the quarq has cadence, but what about speed? Do I just rely on the Garmin for satellites for speed?