The type of improvements you will get from a better arm/table/cartridge are, you again hear many new things that you cannot hear now, from the bottom to the top including soundstaging, with less record noise.
I don't know the price range you are considering. However as far as the arm and cartridge are concerned I would suggest the Origin Live Silver arm with a shelter 501 mkII put this on a Teres 150
http://www.teresaudio.com/t-150.html
and you will be set for life, and never look back. Your Benz will work with this combo until you can afford a shelter.
The front end is were you should spend you cash.
You can spend a little less and get less performance, that will of course better the mm7 combo you use now, but doing it right the first time is money in the bank, and a lot less frustrating.
I believe this to be the best combo for the money by a vast margin, and will probably be very close to, if not in the same class as the TNT HRX
I don't know the price range you are considering. However as far as the arm and cartridge are concerned I would suggest the Origin Live Silver arm with a shelter 501 mkII put this on a Teres 150
http://www.teresaudio.com/t-150.html
and you will be set for life, and never look back. Your Benz will work with this combo until you can afford a shelter.
The front end is were you should spend you cash.
You can spend a little less and get less performance, that will of course better the mm7 combo you use now, but doing it right the first time is money in the bank, and a lot less frustrating.
I believe this to be the best combo for the money by a vast margin, and will probably be very close to, if not in the same class as the TNT HRX