Welcome to the board.
I have the Bose system in my current car and had the standard system in a coupe I owned for 77 days while wainting for my current car. Many people, especially younger ones, find the bass lacking in either system. I find it somewhat lacking myself, but not too bad. The treble response is fine to my ears.
The Bose bass module is located between the right quarter panel and the right cargo compartment wall. It is not ported into the cabin so the bass is trapped in the rear of the car.
Many people have swapped the Alpine cassette headunit for the Becker Audio 10 single cd player headunit. This is an optional item in non-North American markets. They report greatly improved bass response, especially in vehicles with the standard system. The Audio can be purchased on the German version of ebay of from Autoclass.net
Some people are replacing the entire system with aftermarket pieces. If you think you might go this route, don't spend the extra money for the Bose. Also, be aware that the Bose system is harder to upgrade. It uses an MB proprietary fober optic protocol to send signals from the head unit to the Bose amp, and the Bose speaker use a non-standard impedance.
If you replace the headunit with a non-Mercedes unit, you will lose the ablility to control the volume and change stations from the steeering wheel buttons. You will also lose the audio related display on the Multi-Function Display. Also you should know that there are only two cd-changers which can be used with an MB headunit. They are the MB-Alpine sold by the dealer and also sold by Autoclass.net and the Becker Silverstone 2662. The Silverstone will not fit in the glovebox where the MB=Alpine is mounted and therefore requires routing of a fiber optic cable to different location.
Please forgive any typos or grammatical errors. I don't have time to proofread this right now.