Lex at MCS is building a set for me as we speak. I would talk to Lex directly about your application, if you're serious about the suspension this is the best.

 

Not to worry. I was in the exact same boat as you are right now and understand the situation very well (I've been *there* and back.). Note that there are still some trump cards left that will make the car even stiffer - in other words, any of the coilovers I listed could be modified to be probably just about as stiff as you ever want a car to be:
1. R comp tire: as you already know will make the car feel stiffer. So Bilstein by itself is an entirely different story from Bilstein + R comp. The latter feels much closer to a GT3 for example.
2. Coilovers by definition allow you to change the "coils," ie springs. For example, while the base rate of the Bilstein springs are 336 front/560 rear. You could change it towards 400/600 by using different springs. This is what I did.
3. Stiffer other components such as the various suspension links, which you might want to consider eventually, will make the car even stiffer.

Keep in mind that although "stiffer is better" holds true for a car at the track, within reasons. If this car is to be used mostly on street, 400/600 is probably about as stiff as I would make it. Where road surface is not smooth, a car that is too stiff could be dangerous. Stiff cars like to go airborne with road bumps, and going airborne and therefore losing steering input in a curve is not where you would like to be.
I have tried different spring rates and tires on my Turbo and could tell you that eventually too stiff of a car makes for a very tough daily driver; a stiffly sprung car feels tremendous in a curve, but the noise and harshness will get on your nerves eventually as a daily driver.

Regarding JRZ/Moton: The key is to get a good setup man. On East coast Michael Levitas of TPC is considered some kind of JRZ guru, and that's where I would go if that's the route you choose. They are close enough in quality: JRZ was started by 3 Dutch guys, the J (Jeremy?) of JRZ left to start Moton. Another guy left and started ProTrac I think. So from JRZ we now have JRZ, Moton, and Protrac. Someone here on this forum tried JRZ (my friend Mike/Gotboost?); he eventually took it off because it was too stiff for his taste, IIRC.

 

It's going to be hard to find something as versatile as you want

I have PSS10/damptronics in my turbo (street car) and koni in my race cars