Don't get the turndown in my opinion. You'll thank yourself in the years ahead. Yes it will be louder because the exhaust dumps out under the cab, so there will be a drone. Still get your MBRP exhaust but get one that exits where the stock exhaust does, or dual it off. Probably more money yes but worth it in the long run. It'll still be loud but not right under your feet annoyingly loud. There's the stacks option as well, but I'm not a huge fan of those unless they are on a straight piped peterbilt with a caterpillar under the hood.
'95 3/4 ton 5.9 - hughes plenum fix - double roller timing chain - flo~pro dual exhaust - original transmission still running strong - 2 inches of lift...and she has a drinking problem...