It's probably a 2001.

In 2000 they offered the CAAD4 in the R5000 model.

In 2001 they offered the CAAD6 in the top model. Sandwiched in there was the 5 (the 5 was the first bike they made that had an integrated headset). The 6 was lighter and had hollogram. As that year progressed, the 5 was the top model at the R3000 level. That was two below the team bike. But it didn't start out that way.

They ran through the 5 and 6 real fast, the 6 only available for a very short time before the 7 came out in 2002..

For serial number ID, this may help.