[WilliamLeonhart]

   
I'm leaning toward returning the X2s at this point. Even though they are tanfastic. The momentum's have the added capability of travel (though I most likely wont wear them out too often) and are more comfortable. They do have that closed sound though (which is why im tempted to give the hd 600s a try). 
 
If I amplify the momentum's too much via the Fulla, is it possible to damage them? 

   
 
Why would you return them for examination?
 
Does the itchiness go away?

The crackles you mentioned. I'm pretty sure that crackling (and "pops") sound is never  a good sign. See if they return in a few days. You should keep headphones at listening level (if you can hear it just fine, the cans can stand it). 
 
The HD600 is significantly more refined than the Momentum, but they do need good amping (not just power but synergy as well).

 

[davidsh]

I think many will agree with you regarding amping hd600 but there are also many that'll disagree.

 

[noname2020x]

A quick update.
 
Through a complicated order of events I have been able to extensively test the Philips X2s, the Beyerdynamic 770 Pros (250ohm), the Seinheiser Momentums, Bose QuietComfort 20s, and the HD600s. I plan on writing my amateur impressions of each headphone as soon as I get the time. 

 

[noname2020x]

Long story short though...
 
The HD600s (with the fulla DAC/AMP) are so much better than any other phones I've tried IMHO.

 

[kapanak]

Long story short though...

The HD600s (with the fulla DAC/AMP) are so much better than any other phones I've tried IMHO.

And they scale nicely as you update your source and Amp I recommend a OTL amp like Bottlehead Crack or Schiit Valhalla 2. Beautiful matches for the HD600/650 and even HD800.

 

[Music Alchemist]

  Long story short though...
 
The HD600s (with the fulla DAC/AMP) are so much better than any other phones I've tried IMHO.

 
Cool, man! I'm getting the beyerdynamic DT 880 Edition 660 Ω (aka Premium 600 Ω), along with the Fulla (it can apparently drive them!) to use with it and my JVC HA-SZ2000. So I've got both audiophile and basshead bases covered. ^_^