Have the k-sport as $1,160 (£591@ 1.96) + tax on their website, still cheapest of the bunch. What jumps out at me are the spring rates 12kg / 4kg seem too stiff, even for a V6. Front with 7 or 8kg on the TS with 4kg rears would be better balanced and streetable. In contrast the Tein's are more road friendly with 5kg / 1.7kg (
156 TS).
d2racingsport.co.uk is down at the moment, but there were a range of springs that could be selected (same but purple and slightly more expensive) I'm sure they could be with the k-sport as well on request.
Unicorse is a good reference for springs, down to lap times around the Okayama international circuit on various set ups.
Street use, linear front, progressive rear
156 : F=7.0kg R=1.9-4.4kg
147 : F=6.0kg R=2.3-3.4kg
Some track use, linear front and rear
156V6：F＝12kg R＝5kg
156TS：F＝9kg R＝5kg
156GTA：F＝13kg R＝6kg
147TS：F＝9kg R＝4kg
147GTA：F＝13kg R＝5kg
Mostly track use, linear with helper springs
156V6：F＝18kg R＝9kg
156TS：F＝16kg R＝9kg
156GTA：F＝18kg R＝10kg
147TS：F＝16kg R＝8kg
147GTA：F＝19kg R＝10kg
Strictly track use, progressive with helper springs
156V6 : F=24-28kg R=12-16kg
156TS : F=20-24kg R=10-14kg
156GTA : F=24-28kg R=12-16kg
147TS : F=20-24kg R=10-14kg
147GTA : F=24-28kg R=10-16kg