I definitely agree with staying away from the metal, and other hard dome tweeters. Stay with soft dome tweeters. Possibly, Spender, and Dynaudio, and others without the metal dome. I've seen this problem brought up a lot of times. A lot of metal dome tweeters have a resonance, that is over 20 kHz. They call this noise ultrasonic, but it sure can be irritating and fatiguing on any gear, to a lot of people. You could see on the Mirage M-3si, it states they must be using a filter to try and tame the metal dome down. Links to tests, and them metioning the metal tweeter problem.
http://www.stereophile.com/content/bw-dm603-s3-loudspeaker-measurements
http://www.stereophile.com/content/mirage-m-1si-loudspeaker-measurements
http://www.stereophile.com/content/mirage-m-3si-loudspeaker-measurements
http://www.stereophile.com/content/paradigm-reference-studio-60-v5-loudspeaker-measurements
http://www.stereophile.com/content/bw-dm603-s3-loudspeaker-measurements
http://www.stereophile.com/content/mirage-m-1si-loudspeaker-measurements
http://www.stereophile.com/content/mirage-m-3si-loudspeaker-measurements
http://www.stereophile.com/content/paradigm-reference-studio-60-v5-loudspeaker-measurements