I like Michael's recommendation to substitute smaller chainrings, except that the standard 130mm BCD Shimano road double can't go below 38T, so you're still looking at a new 110mm BCD crankset (cranks and rings). However, if you keep your current 14-tooth(?) chainring drop with something like a 48-34 or 46-32, you may be able to use your existing rear derailleur, cogset, shifters, and BB. I run top gears of 48/13 = 52/14 on two of my road bikes and have no need for anything higher.