get the offroad x for the volume sound you want with your packs. it'll be loud as F when you're on the gas. and 2nd choice would be an offroad H....i just got mine installed with the packs and it sounds badass

deepest rumbly tone i've heard outta the mustangs in my area and it still screams at higher rpms. Its deep all the way up 2800rpms then starts making loud crackles almost like gun shots up until 3500rpms, then it goes back to the regular deep tone until you get into the 5k range where it just screams bloody murder. But for you, i'd say get the slp offroad x. you'll be happy with the loudness. It'll be really poppy and crackly but loud as F.
DO NOT get a prochamber...they're much too quiet as the chamber acts as a 3rd muffler. Awesome sounding tone, but you'll be disappointed by how its quieter than a regular o/r H and X pipe. Hope this helps.