Well, I pulled the trigger..

[eslai]

The difference in mass can also be shrunk a little bit when one calculates the weight of the tires into the overall weight. 18" tires are going to be a little less heavy than their 17" counterparts, if the other dimensions are the same.

I wouldn't stick with the 17's, myself.

[z12358]

Congrats, John!
Keep the 18s.
Z.

[chiefsalami]

Congratulations! I'm almost identical to you in my cars, except a generation back in each case. I have a 2002 Boxster S and a supercharged 2004 VW R32. In my case, I definitely like the styling of the older better than the newer. Just my personal preference, though.

[John Y]

Thanks everyone, for your enthusiasm and input; I'm keeping the Boxster logo, and I think I'll leave it in the stock color. Still on the fence about wheel size, though from the weight info in this thread, it doesn't sound as though I would notice the increase in rotational mass with the 18s. I may need to try to set up a back-to-back drive with my dealer...time to give my salesman a call anyway and see what the cutoff date is.