I have a Rokk Tech Silent Might muffler (Same as a Donaldson!) and really like it. The design of the muffler makes it real easy to use a bypass 'baffle' so I can have a selectable muffler. So far we have really enjoyed it with the factory resonator still in the tail pipe.

We just brought home a toy hauler and I was thinking to myself that the exhaust was too loud. I asked my boys for their input and they both said it was fine. Later when one of them was driving he said it was too loud. Turns out there is a resonance in the driver's corner of the cab (I think it is because that is 'opposite' from the exhaust pipe tip . . . ). After a while it is too harsh. . . . But mind you only when towing that big beast of a trailer.
What I recommend is that you put your exhaust together with those wide band clamps like the big rigs use. If you ever want to change your system around, all you have to do is loosen the clamp and take it apart. Sure beats the u-bolt clamps or welding for getting it back apart later to make modifications.