As far as the detail retrieval is concerned that all comes down to the DAC and a transparent amp section. The implementation of the PCM1792 DAC in the X5 has been noted to be very close to the AK240 (dual Cirrus Logic CS4398), and hits way above its price. It can play 24/192 FLAC files with ease and also plays DSD (not native, converted to PCM). For a DAC the X5 has it going on!
For the amp I find the X5 to be underpowered for my headphones. I like to get the dynamics really moving and prefer a more powerful amp so I pair it with the e12. This is good enough for me and I love the combo, but I know there may be better solutions out there. With the specs of 65 oHm impedance on the 1840 and an efficiency rating of 96db it sounds like you also would prefer an external amp. The Vorzuge Pure ii reportedly sounds great and has good synergy with the X5. The e12 is more powerful and very transparent with a great bass boost. Perhaps Duncan will chime in as he has had both and has stated that he prefers the Vorzamp.
I might also add the ifi iCan-Nano to the list if you're looking for a 3D like soundstage. Their 3D holographicSound setting has had rave reviews and apparently is pretty impressive, as is their Xbass toggle.
The biggest benefit of the AK240, strictly speaking of SQ, over the X5
to me (other than UI) is the balanced output. The only thing in the above list that'll do balanced out with the X5 is the Chord Hugo with its coaxial input. However we're now talking about $2500.
Edit: Just to be clear the Vorzuge Pure ii does not have a DAC in case that's what you were asking. IMO you won't find a better DAC implementation than on the X5 anywhere close to its price.