Seems to me as though your car is plenty quick! When I first got my C280, I wanted more horsepower also... but now I have really come to appreciate the power that I have! And it's not slow... I get to 60 mph in 7 seconds easy (well barely
).
You don't need to be going too fast... I love flying away from stop-lights... but how fast do you really need to zoom away?!
You have a great car... I'd keep it that way! I have added a K&N air filter and I felt as though it revved easier/faster at higher RPMs, but this is unconfirmed. I would give it a shot if I were you... but I wouldn't start cutting away.
There are better things to spend your money on... such as fixing problematic areas of the car (top end rebuild...? interior touch ups?).
Whatever you decide, I wish you the best.