I have that exact exhaust on my 03 Cobra (minus the cats now). I ran it both ways, loved the sound with the cats, wanted it a bit louder so i took them off. The car truly screams now with out the cats.
The borlas really will sound great. Was the best mod ive done so far on my 03. I have since added a Bassani o/r x and the car sounds mean as hell now :D :D