I have an 08 2500 and I'm going to go turbo back with stainless. Should I go 4 inch or 5 inch? I've heard that if your truck isn't pushing 600+ hp that 5 inch will actually rob you of hp. Also does the different brands really make that big of a difference in the sound? I want a deep low sound. MBRP exhausts sounds good on youtube, but other than the muffler being different isn't the systems just pipe?