These are both $70 at nashbar. I need to replace a bontrager racelite that's flaking on the inside of the chain rings. I keep reading about the truvativ coming with a bb - is that just assumed even at this price? Anyway, will I need to change my current bb to put in either one of these? I'm a student without a lot of cash, so if I could keep my current bracket around for a while that might swing the decision. Thanks.