The PowerDrive with I-pilot is a good choice. You'll love the spot lock and the I-pilot trolling features (autopilot, Cruise control, record, etc). I've had Terrovas for years with almost no issues and the PowerDrive is a similar motor. I actually bought a PowerDrive for a Jon boat I'm working on. The GPS puck you've seen is a bluetooth heading sensor and only necessary for the spotlock Jog feature. It's a cool feature but not required. Go to the Minn Kota website and there's a wealth of info about the features.
Chris