Actually, the BOV adapter was my first "sound" mod I did. It sounds just fine and it would impress everyone at shows. It's stupid loud and a lot of people loved it.
I actually just got my Cat back shortly after new years. With a Cat back, it compliments the car so much better...because noise! But with a stock exhaust, it sounds fine provided you can live with that loud PSHHHHHH sound. I most certainly can and have enjoyed it since I installed it.