Thanks to all for quick feedback/answers, especially to the "mysterious" :~) Detlof. I have never heard anything but superlatives used to describe the tweeters (and for that matter the speakers they are usually housed in).
Greg: I am with you Greg, extremely knowledgeable - I am sure I am not alone in appreciating his wealth of knowledge and experience, and more importantly, his willingness to offer it. [:-)] The "mysterious" was an allusion to a previous poster's "mystical Detlof" - unfortunately I was asked to burp a baby before put in in a 'smiley' and found to my chagrin it had already been sent sans smilies. Got one from the baby though...
Detlof: Thanks for being so helpful, yet again. Your offer of assistance is very kind. I asked #3 in part because I am looking for a fair "valuation" as I have found a pair of "essentially unused" used TW1S for ~$2500 and am wondering if they are worth snapping up.
Another question: It is my understanding that they have their own amplifiers built in. Am I mistaken? If built in, how are they? and if not, what would one use to power them?
Thanks, Travis