from TN to Moab you'll have no problems getting that out of a set of 606's. There are two places in Moab. Moab Powersports
and another place. Call ahead to get the tires and other things you want.
I liked having fresh tires at Moab as this is where things get fun. Well a little before that but a good place to stop. You can do TN and CO with 50/50 tires unless it's muddy. After CO I'd want something a little more aggressive.
OH and again put on new STEEL chain rings and chain before leaving. They will last the complete trip, oil the chain every day.