If the unit is preowned, they might not be willing to sell the two units separately. I would price a different frame before I made a decision.
I have a 12' frame for my Nolting. I lose about 6~7 inches at each end for the Nolting head room, but that leaves me almost 11 feet which will do over a 120 inch wide quilt. It's the biggest I think I will ever want to do.