Can I just replace the speakers in the coupe? keep the stock amp. are there any speakers that will just drop in?

 

The speakers in this car seem to be of the normal ~4 ohm variety. So you can pretty much replace them with whatever you want. There's a nice faq here about installing Polk EX3500's

<a href="http://www.6mt.net/forum/topic.asp?TOPIC_ID=3417">http://www.6mt.net/forum/topic.asp?TOPIC_ID=3417</a>

I haven't gotten around to replacing any speakers yet, but I did replace the Bose amp and installed an aftermarket amp and EQ using a Peripheral Ven4 that I picked up off Ebay for $10. The difference is amazing.. If you EQ up the highs you can finally hear the tweeters and they don't stink as bad. I later added a pair of 10 subs to the mix and it really sounds incredible. I'm used to adding subs to cars that can't get the fairly low frequency response that the G35 has "built in" from the factory 6x9 "subs". The result of having the existing stuff plus a real pair of subs for sub-bass is very pleasing. I'm sure when I finally do get around to replacing the front door speakers it will be insane. The existing Bose stuff in the back will probably always be sufficient for my needs, unless I blow them or something.

 

Better bang for your buck is to leave in the speakers and replace the amp. I am running 100 by 4 to the speakers, 150 to the 689's and 700 to a 12w6 JL and I think the system sounds great, plus i didn't mess with all the door panels and such.