I called Amsoil Tech Service and asked them about their Absolute Efficiency line with regard to the parameters you guys have dug up. The filter listed is the EA15K20, which is speciifc to the S2000 (it's not the same filter listed for every other Honda, as a lot of other filter manufacturers spec). It directly cross-references with the WIX 51334.
The only parameters they would let go are the By-Pass Valve Setting: 11-17 psi, the burst rating: greater than 360 psi (they said they couldn't get one to burst in testing), and the nominal micron rating is posted on the site: 98.7% at 20 microns.

I've used the 15400-PCX-004 filter since day one. But have wondered if it would be advisable to use a quality aftermarket filter - and which one is the best choice. The Amsoil filters are high quality - similar to the M1 filters, and are very efficient at filtration. Let me know what you think.

http://www.amsoil.com/storefront/eao.aspx

 

Just remember that the bypass valve opens once differential pressure gets too high. The absolute value of the system doesn't matter, only the difference between input and output pressure. Any filter with about the same amount of flow/ filter area (or larger) will work as well as the OEM filter. Of course the media quality is a factor too.