For a 110 BCD (Compact) crank, you are limited in the smallest ring- 34- that you can have. But for the outer ring you can get many different sizes from 38 to 50 and beyond. There is a compact triplizer available from Origin8? that will replace the inner ring and add a standard 74 BCD granny ring, which can go down to 24 teeth. But then you'll have a triple crank, and need a new derailleur, shifter, bottom bracket, etc.