In the interests of sharing something I've found
useful...
I'm a middle of the pack rider, 18-20mph depending
on distance and terrain, and spend most of my
time in the 53 in front and 15-21 in back. I've
long been a fan of Shimano's 13-23 cassette (105 level)
since it has an 18 tooth cog (1 tooth jumps from 13-19)
giving me very fine gear choices in the range I normally
ride. I've recently jumped onto the "compact-crank"
bandwagon and bought a Ritchey 50-34 crankset. With
the Shimano cassette these cranks rock! On the flats
I can now use 13-15 and, with the 34, I get 1 tooth
jumps in the back on climbs up to about 6 degrees before
I have to use the 21. A very useful setup and
/much/ cheaper than DA 10s.
Bob