would make the Z1 make it worth it. If you can make a 3" cat back system better than Z1's, go for it. Most would probably say that 600 is an attractive price that is hard to beat, so your time and effort might not be worth the outcome unless you are really talented. Most all of us have some project that we want to personalize our Z with that doesn't come from a box. If you feel like you can create a high quality exhaust that suits you, go for it.