Just installed rear speakers

[MrPegazus]

Well I´m all new to this forum, just bought my first Boxster today. It´s a -99 with a totally original Stereo in it, no speakers in the doors or anything.......and EVERYTHING feels great about the car......except for the awful stereo =((

I just traded in my BMW 523 Touring with MB-Quart speakers, Sub and everything...and I feel that I really have to do something here......

So what should my first thing be (without rebuilding the entire car ;-))
Easy tips please: Change stereo, change speakers, putting speakers in the doors or behind the head??? A sub somewhere??

All suggestions are interesting, Í'd really like links to "do it yourself" -sites or so.....or just tell me what You have done!!

Thanks