I'm buying a radio nd some speakers but I'm not sure if I need a install kit for the radio nd I don't know what size speakers to get for the doors...

 

No radio kit needed for the headunit you will buy. It will come with two right angle brackets. You screw on side to the HU and one side to the factory screw holes. For the speakers you will need 6 1/2" mids and 1" tweeters.

Here's what I bought and they sound amazing!
http://www.amazon.com/gp/product/B00...?ie=UTF8&psc=1

You will need a spacer for most aftermarket door speakers for the 6 1/2" mid to clear the inside of the door. About 3/4" spacer is sufficient and easy to make your self or to buy.

 

Ook kool thnx

 

A couple of things -
if you want your dash controls to work with an aftermarket headunit, you need to buy a headunit capable
of some sort of remote control, either IR or hardwired, and a dash control interface (DCI) to translate
the dash commands to the headunit. There are others, but the most popular is the Modifry DCI.
In addition, you'll want an adapter harness such as Metra 70-1721. Be aware that many of these don't
have the S2000-specific dash wires, so if you intend to use a DCI, buy Modifry's adapter harness which
certainly does. You may also want speaker harness adapters.
Finally, most headunits don't come with the above-mentioned brackets, but you can reuse the ones that
are bolted to the factory headunit.

 

...and if you want a really install then get Modifry's PnP harness (only available for a couple of brands of head units IIRC).