I don't think there is a big difference in sound between those tweeters and other speakers. I have Hsu HB-1's which use very similar, if not identical tweeters, and they don't sound that radically different. A bit stronger dynamic response, if anything. Lots of slam for home theater and percussive music.
The extension on those speakers probably aren't measured the same, so they don't mean a lot. I know the Infinity speakers do bass pretty well, because I have a pair of those. Those are very highly regarded speakers in their price class. I suspect the BIC's would do bass well too, what with two 8" woofers in a pretty good sized cabinet.
Both the A6 and the EMP speakers have been reviewed by Audioholics, and the bass was said to be insufficient without a subwoofer. But otherwise they were said to be very good speakers for their price.
Your safest bet is the Infinity speakers, but I think any of them will be very good. Your low range kind of goes to waste when you get a subwoofer, depending on where you crossover the speakers at.