What kind of sounds you want, what kind of performance and how it will look. This blog will be rather brief since choosing an exhaust really depends on your personal preferences. I'm just giving my opinion based on what I have done to my car and what I've seen others are doing.
To kick off, let's focus on the rear of the car, particularly the exhaust tips. While the AMG-inspired quad tips may hold a certain allure, it's essential to be realistic about the C250's performance capabilities, the C250 will not be as fast as the C63. Unless you're planning on an engine swap, the quad tips can create an impression of power that the car may not necessarily possess.
In my opinion, opting for a dual tip setup, similar to the ones found in the C300 and C350 (which happen to be cars you can actually compete with at basic stage of mod), is the way to go. To achieve this, I recommend acquiring a diffuser from a C300 and pairing it with some stylish 4-4.5 inch exhaust tips. This combination will provide a sleek and refined look to your C250 without creating a disconnect between its appearance and performance potential.
Moving towards the mufflers I noticed that a lot of people do a muffler delete to reach the desired volume. However by completely getting rid of mufflers you are getting rid of the much needed back pressure the small IHI RHF4 turbo needs. My recommendation is going with at least one muffler around the middle or 2 mufflers in the back, like in the C300/C350.
Further down the exhaust you would see your 2 resonators. Most people completely get rid of them as well. While it will definitely increase the volume of your exhaust it will also add droning at the 3-4k RPM range. In my setup I went with one small resonator and it still has a small droning issue around that RPM range. However I would definitely recommend getting rid of the resonator closest to the CAT to free up the flow and make it sound louder. ‘
And perhaps the most controversial part is the CAT. We all know that we need it to pass SMOG and clean up the exhaust but to be honest a catless downpipe is one the the best ways to improve sound and add a touch of performance. The turbo lag goes away and the car feels much more snappy. I would recommend this mod on your own discretion seeing how some states don't allow catless downpipes.
As long as parts go I decided to go with a dual tip setup going into 2 magnaflow straight through mufflers, into a Yonaka resonator and an Armytrix downpipe to top it off. After comparing the sound and performance of this setup to a more common straight pipe axle back I found the car to sound and perform better due to better throttle response and lack of unwanted sounds