Just picked up a great little Trek 2300 for my daughter in a 50cm size. It is all Shimano 600, which is a 7-speed system. I want to up-grade to STI shifters and am wonder what all I need? Based on my very limited Shimano knowledge, I am guessing that, like Campy, a Shimano 8-speed fits in the same width as a 7-speed. Is that correct? That I will need the STI shifters (duh!), an 8-speed cassette and the matching 8-speed rear derailleur and chain. Is my guessing correct? Thanks for your help and have a Merry Xmas!!