I am new, don't know much about Bikes. I'd like to get a fixed, but was unsure on the difference between the base Kilo tt and the Kill tt pro?

Bikes direct says its the wheels, chain, ect...but how much of a difference is this really? I am going to use the bike for commuting from school and back, occasionally long distances.

Also, should I change out the rear hub to something better, like a 16T?

Where do I buy replacement parts: bars, gears, ect?

thanks for your help!
-Nick