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
Ok guys, thanks for replying
What about sample rates??? 
If I play 44.1 kHz songs, they shouldnt have any ultra sonic frequencies, isn't it? 
Any thoughts about this subject??? 
Roberjeman you are the kid who called out all the royalties’ new and old clothes here. All psycho-acoustics. Unless we are looking at Lowther or Diatone that measurably roll off at 8k supertweeters just give confidence to the listener. Most people don’t realize "air" is at around 3-8k and not the upper extreme. In case of realistic in-room compensation of full range drivers, people often buy a superduper tweeter of some 98+dB efficiency and cross it -6dB per octave at 15k, not knowing that at one octave below: 7.5k, the tweeter still blasts out 92dB of "air" and that’s what they are hearing.
The original "super" tweeter was the Janzen D-130. Four electrostatic elements in a horizontally-angled array with built-in crossover. I have a restored pair! Designed by Arthur Janzen to be used atop the AR's and KLH's of the 50's and 60's and improve the speed and dispersion of the top end!