OEM NSX offsets from the wiki:
15x6.5" +55mm (205/50R15 @ 33psi)
16x8" +60mm (225/50R16 @ 40psi)
Going to 15/16 really does help the feel of the car: in a non power steering NSX, steering effort feels lighter and has a...nicer ride, suspension seems to "work" faster.
IMHO, there is no reason to run a larger wheel than what came OEM unless you are running bigger brakes, besides looks.
The SSR are available in 15x7 +42 and 16x7 +42.
FWIW, and at the risk of sounding like a shill, D-force can make custom wheels, but their MOQs means needing at least 50 people interested for a set. Custom means correct bore sizing so no need for rings, either.
http://dforcewheels.com/pages/products.php
Sector 111 OEMs wheels from them for their offering for the Exige.
http://sector111.com/products/performance/wheels/coming-soon-ethos-wheels.cfm
With the number of OEM 5 spoke wheels out there and their price, it's the way to go. The one thing I'd like to see would be a center cap that just covers a bore for the OEM 5 spoke.
(edit: not my car above)
It's a good look. But given how far the hub sticks into the bore, it will be practically impossible to do.