Will turndowns affect the sound of cut-offs???

Before the 95gt I now own, in 2001-2003 in had another 95gt with a similar setup. BBK headers, BBK h-pipe, and single chamber borla's. It sounded crazy loud, as I'm sure yours does. At crusing speeds, my turndowns sounded a bit how you described, like my uncle's 1977 F-100. When I actually first cut off my pipes, it sounded like an old truck to the extreme. When I put the turndowns tips on the mufflers , it took away some of the uneven-sounding burble found on really old cars, but still was REALLY loud and deep.
As far as performance, with the H-pipe on a mostly stock motor, you will notice a bit less low end (I mean real low end like 1000-2000 rpm's) but you will have more top end. 3:73's with that exhaust set up will be perfect. Good luck!

Check my sig for my exhaust setup. With mufflers open (bypassing the mufflers) it sounds loud and throaty as hell.

JJ