There's a lot of douche-baggery and misinformation in this thread.
First. Swift Spec-R spring are indeed progressive.
Swift Springs USA
Their metric coil over springs are not.
Swift Springs USA
"Spec-R" is a product. Swift makes a Spec-R for a lot of different vehicles. The Spec-R for the 370 is not the same as the Spec-R for any other vehicle.
That being said, OP. Do not go to the Nismo suspension. Don't waste your money. Figure out what you are going to do with the car first and then put a budget together. Suspension is expensive, and you get what you pay for. The more you pay, the better it gets.
If you are on OEM suspension, the best bang for buck you can get is a new front sway bar. Buy a Stillen, set the front full stiff and the rear full soft. The next best upgrade would be either a 1-way coilover+springs, or if you don't want to learn about springs then just buy Koni yellows + the Swift Spec-R springs. You won't be disappointed with any of the above. The nismo dampers and springs are nothing special.