idk if there is a differance between the ram 4.7 and the dak 4.7 but ive got borla and it sounds kickass. if i had a ram though i would have gone duels out the back rather than my side exit. i took both resos off, but here in this vid i still had 1 reso on. once i took the 2nd one off, it was quite a bit louder (especially at idle and low speeds, it sounds a lot better i guess i need a new vid) but at normal driving speed the sound in mild. it really opens up when you stomp on it. the revs in the vid are to 4k (at least the 2nd is) i love the sound, but if your trying to be the loudest, then borla isnt what you want...anyway, its got a real nice tone, enjoy
and to answer your concerns about performance....if you want performance over sound, your best bet is to go with a packed muffler (magnaflow/borla) over a chambered (flowmaster)....the pics below prettymuch explain themselves
packed - the airflow is almost undisturbed, and the contents which is used to pack the muffler distinguishes the sound...its normal for a packed muffler to sound a bit louder after a week of driving than right after it is unstalled, but after that prettymuch no change. idk why that is or at least i havent been able to find/figure it out. i know the stuff in the pic looks like it will heat up and burn out, but ive had no problems
chambered (sorry for the small pic) - you can see, the airflow is disrupted, even if it was a center input and a center output rather than staggered.
in fact, many people with chambered mufflers actually see a slight decrease in performace but not all, its offten too minute to tell...im no expert, but its just what my readings have found and it makes sense to me