I thought that I noticed the same thing. I went through the 'build your own' page when I was waiting on mine. But I tried it a gain a while back, checking to see if there were any price increases, and I did't see the SGII alone, wo/Nav. I thought that maybe I just missed it.
I have a 2006 with SG II and no nav. Ordered much earlier in the year though. I now have some regrets about not getting the Nav though. I think it will be an expectation in a few years when I sell this one.