Well all and all the C5 brakes are the same size caliperwise so you wont see any additional benefits except maybe easier to find. I have an upgrade for the Catera ready to sell soon and it will be all the things you need for the swap... just give me a few more days to finish the work...
Also currently on ebay there is a complete set.. but it will run you 100$shipped and it includes the rears as well... You can use those but I'd rather stick with my dual piston non floating calipers back there...
http://cgi.ebay.com/ebaymotors/2004-...QQcmdZViewItem