welcome to the site. There is a lot of info around the site about the new civic/ civic SI. If you have a specific question - just ask! A lot of info is known about the car by quite a few members on here.
I thought that the 2005-2006 RSX-S held a K20Z1, or at least for 05 it had. And I thought the 06 Si was to be a 1.8L which means if they are only manufacturing them for Japan, there will be no major difference between the 06 RSX and the 06 Si (USDM)?