Im going to replace my rear muffler with a magnaflow muffler. The one that magnaflow uses for the jetta catback is 5x8x14. I was thinking about a 5x8x18 after hearing that the longer the muffler the deeper the sound. What do you guys think? Also, will replacing just the rear make a difference in sound? Should I replace the mid muffler too? I was going to get the magnaflow catback, but cant justify spending that much (also, dont have that much) for a catback exhaust that is only like .2" bigger in diameter. thoughts? any help is appreciated.