The LazyAssGeek’s

Whether or not a straight speaker swap will be good enough for you is entirely dependent on your goals. If a modest improvement with some real highs is good enough, then what I recommend doing is replacing the 3.5″ speakers in the doors with a coaxial speaker like the Boston, Eclipse or Infinty that have been used many times around here.  I wouldn’t worry about the dash speaker or the rear speakers until you listen to the results of replacing the door 3.5′s.  If you like what you hear but you think it could use a little more, then perhaps replace the dash 3.5″ and the rear 5.25″ speakers, but you won’t get much more out of doing that.

Forget about replacing the door subs.  The door subs on the Bose are self-amplified so you would also have to install an amplifier to drive any replacement speaker you put in.  If you have non-Bose then the problem is that any good sub you put in there would require a great deal more power than the stock amp is capable of delivering.

However if you want TRULY good sound… the bad news is you have to start all over and install an amp, put in a good set of components and probably a sub.

Just in case…. I haven’t laid hands on an ’08 yet, but all indications are that the stereo setup is identical to all previous C6′s.