I guess if you have Campy road bikes, It would make sense to build it with Campy.
If buying new 2007, I'd get Chorus shifters, centaur or veloce UT cranks (the only difference is color and the machined vs stamped rings, but if you are going to change the 50t to a 48 or 46t might as well take the cheaper veloce crank), centaur or veloce cogs, veloce chain, spooky brakes, veloce rear derailleur (no carbon) centaur or veloce FD.
If you want to save money, hit up ebay for pre-2007 shifters.
I'm building a cross frame now and I'm really torn on what parts to use on it. My road bikes are campy and have 1 spare rear campy wheel. I really like to try out SRAM since the wholesale cost on it is so low but i'd have to buy/build new wheels.