I'm not sure that I understand the questions fully.
A 9-speed crankset and chainrings (6500) will work with a 10-speed drivetrain.
The shifters, cassette, and chain all need to match, 10-speed to 10-speed (6600).
9-speed derailleurs will work with a 10-speed drivetrain.
10-speed derailleurs will sometimes work with a 9-speed drivetrain, but there may be problems, especially if the crankset is a triple.
10-speed Ultegra shifters are double or triple specific, 9-speed Ultegra shifters go both ways.
Al