Recommended systems - components for Car Stereo

Russellb - 90% of the quality of sound you get in a car is the installation, 10% are the products chosen.

You could drop in some new drivers and a head unit for $1,300, and this will be a starting point, but will likely still have huge problems with the sound, and will leave you wanting more.

If you are used to high end home gear, trying to even get acceptable sound in the car (especially a small one with a soft top) is going to be a challenge, and likely cost much more money than anticipated.

Your best bet is to try and find someone with lots of experience making cars sound good. Make sure you only believe what you hear IN CARS (not in a soundroom), and also don't believe car audio dealers claims until you hear results, as many that I have run into are snakes.

How the drivers are mounted and damped in the door panels is of extreme importance. If they are mounted to a floppy piece of plastic or vinyl then the sound will be dreadful as would any home speaker. MDF pieces mounted to the door frame, with fiberglass and other absorption in the door panels is a must.

Ideally, you will want to take the drivers out of the doors, and put them in kick panels so they can be more angled towards you.

Anyway, good luck!

Thanks Goatwuss - unusual name by the way must find out how you got it. My research so far has reinforced your advice.
The custom installers are looking an average of 4K for a system using their experience. I cannot warrant spending 4K on a ragtop due to its limitations.
This lead me to visit all the BMW blogs to see what other M roadsters / Z3 owners had done and most say the compromise for the money is to keep the locations for the main speakers since this was engineered for the best audio in a ragtop, but upgrade them. The biggest upgrade for the money being the Amps - One for the main speakers and one for the sub. This is then followed by changing the 5.25 inch kick panel speaker and finally the door mounted treble/mid speaker.
So the amps are easiest for me to select (power ratings, matching) then the speakers,
So I am still after recommendations for Speakers.
I order of preference of other peoples systems I am leaning towards AVI MXD 130, MB Quart Premium line, Polk SR250 series.
Any other recommendations for speakers ?

Russel,

For speaker drivers, I would look into Dynaudio, Focal, Scan Speak or Morel.

For amps, the JL amps are an inexpensive and good way to start.

Would your plan be to use your existing stock head unit? Oftentimes, the stock head units will have built in EQ for the stock drivers, so you'll just want to make sure that this isn't the case.