I have been practicing throat singing on and off for over ten years. I can achieve the high whistling tones and the sub-fundamental "deep voice" as well. There is no way to describe how it feels to produce these sounds with your own voice. I've played around with beat-boxing but I never took it to the level as some of the people in these video clips. The range of sounds we humans can produce is amazing.
The interesting thing about throat singing is that it is all harmonics. One book I read on the subject said that a singer can't produce a certain harmonic until they can hear it. That made me think really hard about deep listening and finding new harmonics in pieces of music I had listened to many times. What is really cool is that you can record the throat singing, then open it in a program like Audacity and look at the spectral view of the waveform. You can actually see the harmonics that you're producing.