I've bought one of these frames (black, red, white) 2nd hand and I was under the impression that the same frame was used throughout the range. Since looking, i've noticed that my frame has a thicker tubeset, especially on the top tube than the pro, race, sl etc and the internal cable routing is only partial.
Not sure if anyone will know, but i'm just wondering why it's a gtc but different to the rest in the year range. And if it won't be as good to ride as the others. I thought i'd got a bargain but perhaps not so much...