Your thin threaded rods are like guitar strings, and one little metall screw nut cannot damp the resonance by open end on top. My Z-Axis with thick rods, plastic nut and bearing on top end: https://plus.google.com/112467558426863470913/posts/P6YRmxUiTFM
@Maxim_Melcher Your setup is quite impressive, on speed and noise level. Think I am going to redesign some of the parts so that it supports a bigger rod and maybe also using a belt same as you do.
@James_Armstrong Thats a good info. But seems that the Pin for that is only on the chip itself. Should be pin 19 on the chip, according to the data sheet. Will test that on one. Have 5 spare drivers as I am actually building two printers.
Correct. I had to solder a thin wire on mine. I have a BeagleBone Black with a Replicape board that has the DRV8825 chips on it and they are noisy and need to make that mod also. The manufacture said he will be connecting that pin to the BBB next time so it is configurable.
@Lukas_Obermann this driver have a adjustable decay: http://www.dr-henschke.de/RAPS128.html
Thank you all for the support. Have a lot of things to try and test now. Will post an update when I am happy with the result 
Like: http://flic.kr/p/eFgNNR
@James_Armstrong @Mark_Rehorst Thats an awesome idea! Good thing i have lots of spare pulleys and around 20 meters of belt laying around. One question, how did you create the “endless” belt on the top? Is it glued together? Or a already bought one?
I am lucky to have a friend around the corner that has every part known to man in his house. Known as “Jetguy” in the 3d forums. We just found one that was close and then used slots for the idlers to adjust the tension to make up for the slack.
@Mark_Rehorst Ok. Thanks for the advice.