Cindy's 30x25 = 32.4 gear inches
V's 24x28 = 23.1
Sarah's 28x34 = 22.2

V and I have several more gears in the low end -- cliff climbing gears. Roughly each 2 inches or so gives you one more gear.

Swapping Cindy's cassette for an XT 9 spd with a 32T cog = priceless . Actually, it is 25.3. A 34T cog would be 23.8 and almost exactly what V is running.

Cindy, Bubba can talk your ear off on Friday about how gears work if you want to get into the physics of it. You can look at the gears we're running also and really see what it looks like. Think of mtb bikes - little in the front and big in the back.