Dear Ambrose: The Tannoy supertweeters are great ones, I own the ST 200.
Now, before you buy any " supertweeter " you have to know exactly what are looking for in the music/sound reproduction of your audio system, you have to define your music/sound reproduction priorities and to have experience with live music. Then you can decide if a supertweeter meets your priorities.
If you buy it, you have to have care about how can blend with your main speakers: crossover points, volumen, position, etc...
Remember that you only know the " presence " of that supertweeter when you disconnect it.
Regards and enjoy the music.
Raul.