Yeah, I'd have to say that setting off car alarms with your system would be amusing at first (I pretty much never play it that loud anywhere), but setting them off with your mids would be quite hilarious. But I'd get rather annoyed with it after awhile, I think.
I don't recall exactly, but I think my comps were hitting around 115-120db without maxing out the gain on the amp (I have no desire to mess with gains now that my system is setup how I want it). Not bad, although I've heard of people hitting 130-ish numbers with comps before.