Buy the bilsteins, put your OEM springs on the lower perch, job done.
Don't waste your $ on the D2/K-sport/Megan coilovers, if you want to search for information on them, go to google and search for "D2 site:nsxprime.com", they're lower-quality systems with too much adjustability, and questionable build quailty. If you want something stiff you can get the custom valved, but there is a reason they're at this price level. Any company that tries to appear to be another company raises red flags in my mind. D2 uses another company's logo to give itself 'racing credit', Megan is an attempt at 'Mugen'
The main question I would pose is do you really need coilovers, or are you going to set them at a specific height and leave them that way? Cost is not a good reason to buy coilovers.