I tried another module which shows the Categories / Sub - Categories, called Hierarchical Category Filter Module (which was good also...)
This module here does not need a "button" to start the search and it shows immediately the sub-categories.
Displays Horizontal / Vertical, and the CSS is a beauty.
The installation is easy and I even translated it to Hebrew (RTL, utf-8) without problems.
The "Accordion" style of the player helps my users to manage their files easily.
The Support I got from the developer was immediate and he help me solve a problem caused by a DIFFERENT extension...
A 5 stars and worth every penny.
It has many options and a very flexible module.
At first - I got a little lost from all the options - BUT - the developer was AMAZING in his support, and solved ALL issues I had with the module!
Thank You Adrian!
I am a happy customer...