ekthrilla

I am pretty sure i have the 50 series flowmasters on my car...i have an off road X pipe and 2 1/2 inch exhaust all the way back... i am wondering why my car is so quiet. my friend has magnaflows and his car is so loud. i cant hear my exhaust over his. if i get 40 series would it give me any more hp gains or would it just be louder or would 40's make a difference at all? i have heard about super 40's but i dont know much about those. i want a muffler that is mild at idle and loud at WOT. what is my best bet of a way to go for just the muffler...thanks