Stand alone tweeters

Has/does anyone use these or anything like it? If I was going to purchase and hook them up I assume I would have to use a separate amp? They are 8 ohms and my Tylers are 4 ohms. I am tapped to the 4 ohm output of my Mcintosh now. The only way I think I could do it is to run the tweeters with the rear L&R of my Harmon Kardon, run it in full stereo mode and adjust the channel outputs accordingly. ( I use the Harmon Kardon as a pre and am not concerned about home theater). What do you guys/gals think?