looking at getting the Garmin 305HR and wanted to know if if comes with the speed sensor or do you just use the GPS. I noticed you can buy the speed\cadence seperate so not sure what the unit comes with. I looked on the website and while I think I know, it's not super clear on the items in the box. Also, please confirm that you do not need to have any kind of subscription service for the GPS capabilities. Can you also tell me if you have had any quirks with it and was the chest strap big enough for you. I have a 56-58 inc chest and while the Polar strap will work, it's tight.