Super tweeters, are they worthwile?


Hello guys
I've been reading some infomation on the web about super tweeters and I've got curious.
First I didnt believe in subwoofers, I thought the would only add bass quantity to my system and then I got convinced and I tried one. Well, I couldnt believe how much it improved the 3D image, making it rock solid and so real. And I thought soundstage was mostly the tweeters job. 
Now I read some guys swear that super tweeters can also improve the soundstage, 3D image and bass!!  Well, If a sub can improve the mid and high frequencies, I think I can believe super tweeters could improve bass. 
First, I would like to now your experience with super tweeters, please only the ones who actually tried them. 
Second, if I listen all of my music streaming Tidal hifi (44.1 kHz), does this sample rate have ultrasonic infomation for the super tweeters to play? If not, does software or hardware (DAC) upsampling delivery it? 
Finally, wich super tweeters would you recomend under 1k the pair? I mean, ready to plug and play. I dont have the expertise, nor the time and patience to build crossovers, etc.
Just to mention, I live in a country where I dont have the chance to borrow them from a dealer with a trial period. I have to buy everything blindly. 
Thanks!! 

plga
I remember the Janzens- but I don't remember how well they cohered with those acoustic suspension speaker designs. I think part of the reason for the use of the Deccas with the old Quads wasn't just frequency related, it was dispersion- the Quad was notoriously beamy in the high frequencies. Head in a vise sweet spot. Glorious when sitting 'just so' but drops significantly if you aren't positioned perfectly relative to the speaker(s). 
I had my Quads refurbished and now use them without any ancillaries. Not an all-rounder, but a great second system. 
Don't know if super tweeters would add to the performance of the other speaker components but the bottom line appears to be what we actually hear.......

Experiments have shown that a healthy young person hears all sound frequencies from approximately 20 to 20,000 hertz.
Some dogs may hear up to 50,000 hertz. So, if the neighborhood dogs start barking while you're playing music then you may be shooting for the wrong goal.


Instead of invest in superteeter invest in a good dac will improve your dynamic , soundstage and seprarste , do a research about a dac and get the one work for your system 
I have used Heil AMTs as super tweeters with good results on several sets of speakers over the years.  With some speakers they don’t seem to make an improvement.   But I built my own crossover and you are looking for something turnkey. I hope you can find ones that you can try without having to keep if they don’t sound they way that you want. Good luck. 
I use the Sopranino’s with TAD’s. The integration is seamless. Imaging and soundstaging are unchanged, but this could vary with placement of the tweets in relation to the mains. The main benefit is the more ‘alive-sounding’ quality that they impart. It’s subtle, which is how they are voiced.  The effect is consistent for all types of music. I can’t imagine how they wouldn’t benefit any dynamic driver setup.