What would be the best way to add Accounts with Subsidiary below an active account without the Sub?

Our accounting staff wants to begin tracking several of our expense accounts by groups. We have proposed using the Subsidiary portion of the Account Master file but are not sure of the necessary setup to get the correct results.

Currently:     130.602     Salaries     Level 6     Post Code blank

Proposed:     130.602          Salaries                 Level 6 ?     Post Code "I"

                    130.602.01     Salaries - Dallas     Level 6 or 7?     Post Code blank

                    130.602,02     Salaries - Ft. Worth     Level 6 or 7?     Post Code blank

Of course we understand that the 602 account would have all the prior fiscal year balances and associated transactions and would need to be Inactivated. The real question is should the Level of the new Accounts with the Subsidiary be at the same level (6) or a lower level (7)?