I've owned many verts. First thing you have to figure out is if the top is fabric or vinyl. Usually Japanese cars use vinyl - but that is not always the case. I've never owned a vinyl top - so I'm speaking from experience with fabric here.
Honestly, unless the top is stained or has mildew, the best thing to maintain it with is just carwash soap. But, I would start out with a deep cleaning a bit different....
If it's cloth, I would go to the local BMW dealer and spend like $9 and get BMW Soft Top Cleaner. Hose the top down, then spray and scrub in the top cleaner. You want to use a medium stiffness brush - something like medium nylon.
Then rinse very well. Once the top is dry, you need to add protection. I'm just going to tell you - I hate RaggTop. The reason is because it's aerosol and it will get on your glass and paint no matter how careful you are. I don't think it lasts nearly as long as 303 either IME. It's also much more expensive than 303 per application.
I like 303 Fabric Protector. But, I don't spray it on. Dump it in a wide mouth cup and paint it on with a foam paint brush. The bigger the foam paint brush the better - as it goes slower than you would expect. Put it on HEAVY. It will look white and streaky - don't worry about that.
After its dry, any "streaks" that are left will easily brush off with a DRY cotton towel. Now it will bead like crazy for at least a year - probably 2.
. Always really liked S2000's. Seem like really fun cars to own. Sorry, can't really give you any advice on the vert top. I'm kind of a rookie when it comes to convertibles.
