keep the gs...you get class, power and more interior space. get rid of the mercedes, which will save your mom the extra $ is she downgrades to another car.

 

If the Benz is paid off this is what I would do. Take all your mods off of the GS. Sell the GS. Get mom the Civic. Sell the Benz, and get a newer GS with less mileage and put all the mods back on. If you work it right you will both have newer cars, and you'll have some extra cash in your pocket for more mods. LOL!

If the Benz isn't paid off...well, I agree with idea that the Benz looks like a girly car to me, and you are going down to a 6 from an 8. I just couldn't do it.

edit: just read through and saw that the Benz isn't paid off. just convince mom to keep the benz. that way you get to have both the GS and the Benz in the family.