A carbon bike will make a huge difference...and even different wheels and different tires can make a huge difference. Going from a heavy mtn bike to a light cross bike can be amazing. A year and a half ago I could not climb a small local hill that I don't even use my inner chain ring on now. The other day I passed a gal straddling her bike, walking up the hill. She cheerfully said Hi...and I almost stopped to encourage her but I was past her before I really gave it any thought. Speed and endurance don't come fast but if you keep at it they will. My big suggestion to everyone working at it is to get a heart monitor and make your riding both fun AND a good, doable aerobic pace which will make a huge difference as compared to just riding easily at too low a pace to really help you gain strength and stamina. A good aerobic pace is, by definition, doable for an extended period.