I have been using a E09K to power my DT990 600ohm cans for over two years now, long enough that I don't really remember exactly when I got it but for sure over two years.  I use this thing every single day for hours each day because it is part of what I use for my work.  It literally could blow my 600ohm cans if I pushed it loud enough I'm pretty sure, I never ever go above half volume because it literally hurts my ears and probably is causing hearing damage when over half ''so I just don't''.
 
Two years and not a problem at all except last night a box weighing about half a pound fell on the power adapter and knocked something inside of it loose, I now have to use a 12volt adapter until I have the time to either fix the 15 volt adapter or buy a new one.
 
I run this in tandom with a Asus Xonar DG, it sounds amazing compared to anything else I have heard for under 1000$ Canadian.  A friend has a Biforst amp and dac and some 1400$ cans I forget the name of to be honest and its the only thing that comes close to what I have on my head and am listening to rite now, for being a 100$ amps combo with 400$ cans and a 40$ sound card this stuff cant be beaten. 
 
On a side note, thanks to everyone here on Head-Fi that told me about this stuff and all the great reviews,  everything I have ever read on this site has been correct or at least personally correct for the person writing a review, because of that I now have had amazing audio for two years and still love it.

I owned a pair of the Z6A headphones and got them to replace my broken Turtle Beach HPA2 headphones. Lets just say I still wound up using the HPA2's two weeks after the Z6A's arrived.
 
Cons: Very poor sound quality, Cheep plastic parts that will brake, Notorious for having lose wires in the cans, The amp picks up interference from to much - ''modem's, router's, microwave and cellphone'' they all cause a buzzing sound in the headphones simply because of the poor quality amp that sits on your desk. 
 
The build quality is so poor that the left can actually broke off of the arm 2 weeks after I had gotten the headphones, Needles to say I am not an Ogre and do not abuse my well earned and payed for equipment. When the can broke off I literally just put it back in the box, then in to the garbage and pulled my old HPA2's back out. 
 
Sound quality: The true 5.1 surround sound I will admit in these Turtle Beach cans aren't that bad, it is more accurate then assimilated surround sound but at the loss of overall sound quality. The sound stage is actually not bad it sounds to me like the sound is coming from about 2 feet away from my head. For 100$ that's pretty good  I think, but the headphones themselves aren't.  The sub bass is very flat, the bass and mids are decent ''for the price'' and the treble is sharp, maybe even a bit bright.  
 
Each can has a 40mm Sub, that kind off adds a bit of a punch but it still sounds flat. As well each can has a 30mm Front, Center and Rear speaker. These 30mm speakers are very tiny sounding to my ears and the front and center will drown out the rear sound so you will have to adjust for that either in your sound cards menu or by positioning the cans forward on your head. 
 
My overall recomendation about these headphones is to honestly just pass on them, if you are looking for a low end surround sound gaming headset there are much better out there, some of the ones I own and or have tried are Logitech G35, Turtle Beach HPA2, Sennheiser HD 350.