I guess if you get that warm and fuzzy feeling knowing that your speakers are playing sounds only dogs can hear then by all means by them. You should be happy your purchase, with no sense of regret.
But first I would suggest playing some test tones through what ever speakers you have and while holding a SPL meter see where the point is that you no longer hear anything vs. the point at which the test tones or speakers cease to play. I can still hear to about 18khz with this non scientific method and I do not feel I am missing anything, especially considering much of the equipment used for playback isn't spec'd for anything higher than 20khz either.
