Mate, please be aware the Nurburgring will be the same as driving on roads (only very quickly)...it is uneven has lots of caber changes and is far from Tsukuba smoothness.
I had HKS hipermax...they were hard and poorly made...one developed a leak very easily after only 8 months ish of use on Brit roads. I then got some ATTKD circuit tune (also HKS) and they were even harder! would have been great on Tsukuba or another similarly smooth track but for roads no way.
I'm now using Tein Superstreets and they are awesome, a great compromise. They are stiff enough for non-competition track work and can be made soft enough for the street. If you want a good solution for both I say don't go with anything that has hard springs...unless you're an all out tracker they will be crap on our roads, causing uneven braking and steering and lack of traction at the rear.
A stiff spring does not automatically = better handling. If you get something like the Tein SS or at the most Flex you can turn them down for street then turn them up on track and pair them with a nice uprated set of sway bars (ARBs) to reduce your body roll on the track (DO NOT use springs to do this). As has been mentioned, one mans suspension heaven is another man's suspension hell but think carefully before spending your cash.
I don't want to sound like a Tein fanboy lol but other units mentioned cannot be serviced and rebuilt over here, and if they're anything like HKS in build quality that's something to note (Wonder why HKS Europe don't support or supply HKS suspension?)
Also as far as I know I wouldn't lump Nismo S-tunes in with all the other units mentioned as they are non adjustable height wise. Basically they consist of a harder lowered spring (non-progressive?) on an uprated shock. I'm not sure whether the shock is even adjustable, I think it is preloaded for the application - pricey for what they offer but they are supposed to be pretty good so if you have the cash then maybe.