help/opinion

ok pretty new to the whole forum dealeo but i had some questions concerning exhaust on my s4, i stopped by a custom exh' place to get a quote on doing some work on my ride, i was thinking i could just have them cutout and replace the stock muffler in the very back, but mr. billy and the shop said since the can was an odd shape and the inlet is in a awkward possition thats not possible, he suggested cutting out the next muffler up and replacing that with a magnaflow then running pipe back to the bumper and throw some tips on it. probably get ragged on for wanted magnaflow but i kinda like it after i viewed some on youtube and im not a bank robber so miltek and awe stuff is outta the question. but what do you folks think of this idea? i'd appreciate any input, thanks