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
The way these are typically deployed can be analogized like running your speakers full range then throwing in a subwoofer. Basically you are running double bass.

A lot of 1" dome tweeters get directional above 5KHz, i.e, they start beaming when you are more than 30 degrees off-axis. Remember basically there’s no real musical output above 10KHz in most instances. It seems the super tweeters function in most cases to simply expand the dispersion of your speakers in the 7-10KHz high frequency range.

It can be useful if your tweeter beams at high frequencies--this will be even more obvious if you have a 1.1" or 1.25" tweeter. However some 1" dome tweeters have good horizontal dispersion out to 60+ degrees and won’t need this. It really depends on the drivers you have.



I recommend a visit to an Audiologist to test your hearing and find out where it drops off!