24t or 26t granny gear? Getting a new crankset, decided on this one from Rivendell: http://www.rivbike.com/product-p/cr1.htm

Question: Should I keep the 24t granny or get them to swap it out for a 26t? I have some concerns that a 12t jump is going to be rather big. I'm guessing either way I will need a chain watcher, correct?

Drivetrain info: I'll be running this with a Sora triple front derailleur. The rest of my drive train is a 9spd Tiagra / Sora shifter set up. 

Thanks.
I have a 12 tooth jump on my granny gear from 30 to 42 and don't have any shifting problems using Shimano 2300 level equipment. A standard compact crank is 34/50 which is a 16 tooth jump, so 12 teeth really shouldn't create a lot of problems.