in 1979 they still used the europa beckers--
much better looking!
yes-- do yourself a favor and install 4 speakers of stock size, all new wiring, a new head unit of your choice, an amp and a single small subwoofer.
itll make a WORLD of difference in how much you enjoy the car!
when i got my 240 i immediately installed new speakers in the factory locations(2 in the dash...) and left the becker, adding an ipod and tunecast.
sounded like...well... 2 tweeters producing sound transmitted over fm radio waves... so i completly reworked it and it is very nice!
links to pics:
Subwoofer box and some images:
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1231232&posts=15
Adding rear speakers and HeadUnit(rear shelf was rotting, had to build one of masonite):
http://www.benzworld.org/forums/forums/thread-view.asp?tid=1223762&posts=7