Flowmaster?

[crew2500hd]

Ordered the flowmaster 50  for my 6.0 2500HD. I am going to keep everything stock from the engine back to the muffler. The muffler has dual 3" ins dual 2.5 out the back. What would be the best setup from the muffler back. If I stayed with the stock SS pipe, I would save money not having to buy new pipes or go with dual 2.5 out the rear wheel. Priced dual 2.5 pipe at the local exhaust shop $160 + tips. Performance wise what would be the best setup. Thanks for the help