I know the folks at CSC offer various sized front and rear sprockets. 14T is front stock and they offer a 13 but not a larger one though I could have sworn I saw something about a compatible manufacture that had one on a thread a long time ago. JT sprockets if I remember right. The rear is a 44T stock but CSC offers up to 46 and down to 42. If you wanted a higher end speed you could stay with the 14T and go to a 42. This calculator will help with what you'll get doing the various combos when it comes to speed and torque:
http://www.sprocketcalculator.com/ Personally I'd think that the bike would be very luggy in 1st gear by going down to a 42. I don't know of any internal transmission gearing that is available. Going to a 14/42 would increase top end speed by 4.8% but if you could get a 15/42 combo that would increase it by 12.2%.
Joe