The S&P 500 index just hit another new record high, but one under-followed stock has been doing even better.The S&P 500 index may have just hit another record high, but there has been an even better place to put your investment dollars. Over the past five years, the total return from GPS navigation and wearable technology leader Garmin (GRMN 0.66%) has trounced that of the popular stock index. And there's good reason to think that record will continue.The S&P 500 just breached the 5,300 level for the first ...