My setup before:
My setup used to be Magic Tube D1 and HD650 which is a really good high end set up <3.
The only problem was that the HD650 have open dynamic drivers! This is almost like speakers so this was the deal breaker for me, the sound can be heard outside of my room etc...
pre iUSB setup:

DacPort LX ---> Uha.6S.MKII ---> UM Miracle
There was something missing and i thought that it is the cables, I tried the Toxic Cable's Copper and even went even to buy the 700$ tralucentaudio's latest cable with the OCC silver +1% gold which was approved by many of my head-fiers friends,
I was mad because there is no way that such a setup can sound so harsh and bright!! and not so 1st Tier nor near my old setup!!!! few head-fiers said they didn't encounter what i encountered what so ever!
you don't know how good, clean and smooth is a setup unless you try something else, thats why anyone with same setup as mine don't know how good is Magic Tube D1 + HD650.( will point why later)
iUSB:
why the iUSB and what made me think about it?
i usually listen to my music on the PC so since my new rig is portable i took it to the collage and used it with my Laptop, i wasn't happy at all , because in the home i was listening to the same
tracks and i was happy with it, so thats how i noticed what can the Dirty Evil Volt can do to our usb powered Dacs!!!! in short moving from dirty PSU to Dirtier laptop made me know the difference!!
how good is the iUSB?
The very first two min!!! it was like a heavy rock just removed from my setup!!! the problem was the PSU after all!!! the Real sound was released from the Jail! and i hear my music the way that it
should sound!
A LOT of harshness is gone! so if you are on a PC most of the time and using usb dac/amp then iUSB is really a must for you if you want to enjoy your music the way that i used to enjoy it with my old setup and the current setup to!
PSU differ from another one:
when i record my voice there is huge Bzzzz and Hsss due the dirty MOBO/PSU provided power, thats why there were few who didn't get a huge leap, because their PC already had a clean PSU,
my PSU is Corsair GS800 which is from one of the best aftermarket PSUs, yet it was super dirty and it was causing a bottle neck case to my setup!
What is a bottle neck case?
if you had a 460 GTX card on an old PC with low RAM/CPU and PCI 1.0, will it perform 100%? no it will show you 20% of what can it do, and this was my setup's case till i used the iUSB
Would i recommend the iUSB?
i really do!!! you will notice the difference!!! we all want cleaner and smoother sound right?