I'm 61 years old and started riding about 6 monthe ago just for the exercise. The bike I started with is a 2011 Marin Stinson comfort "hybrid". All riding is on paved roads. I feel like I'm ready to move up to something better but I really like the way the Stinson feels and rides. Any thoughts on upgrading the components to improve the performance and longevity of the bike? Willing to spend up to $500. Thanks for any help.