06CivicSI, You could probably buy a brand new XF Limited for about the same price as you paid for your SI, a roadster will naturally cost ya a little more.
The difference between the Crossfire and your SI is noticeable, but then you already had a SLK230 so you know what I'm talking about. But with the 320 engine the difference is even more pronounced.
I'm more of a Honda man myself, (I wish I could afford to buy yours) and I recommend Honda to just about anybody who asks my opinion. But the Crossfire is on an entirely different level.
It probably isn't any faster in the 1/4 mile than your SI, but that's where the similarity ends. As much as I like my Hondas, I "love" my Crossfire.
Normally, I would probably suggest to someone like you (who already owns a Civic SI) to consider a new S2000. But as nice as those cars are, they just don't have the "head turning" ability of the Crossfire.
When it comes to reliability, I'd have to say the Honda probably has the Crossfire beat. And before everybody on the forum jumps on me, I'm only saying that because I've driven over 1/4 of million miles in new Hondas, and never had to take one back for any type of warranty work.
The Honda is a car that you can feel perfectly secure with, the Crossfire is a car you can be "passionate" about.