Is this thread officially dead?! I have the same exact same bike, trying to modify it now as a commuter (it's 3 years old... the cassette and chain are more than likely worn by now) and was going to ask about which brake calipers would fit. The brakes are awful as you mentioned. I was told 28c tires can fit on this bike, but unless I can move the calipers it'll be really hard to do this.
Cheers!