Ok after about 4 days of having my car (92 s600) I finally figured out that it looks like 2 of my speakers are out ( front drivers dash, and rear passenger door speakers) so now I'm wondering first, should I take the car to a reputable stereo shop and have them listen to it and tell me what they think? Next should I replace those 2 speakers with aftermarket speakers? Should i replace all 11 speakers?

Sidenote: Im definitely looking for best sound and seen a few people put some after market speakers in there and be very happy, I have also heard that the bose amp in this car causes problems, but would that cause only 2 or so speakers not to play ( actually plays but shuts off at various times) I figure I could probably replace 2 speakers with aftermarket speakers and labor for about 200-300 bucks??

So any advice would be greatly appreciated.