Features aside, would you say there's an actual difference in SQ (Q1 MKII versus Q5)?
I'll be pairing one of them with my iPhone 6s + HD600.
Comparing the Q1ii and Q5 with really neutral IEMs (single ended) - using the Alclair Curve. Digital source is an iPhone SE. Output is volume matched to within 0.1 dB using a calibrated dB meter.
Once you're volume matched there is hardly any difference. Both have very good overall resolution. If there is any difference (and this is marginal - at least to me), the Q5 might be ever so slightly smoother (slight tinge of warmth). But it may well be placebo on my part.
Single ended with the HD600 (I have no balanced cable) - and I again personally think the difference is very small. Both sound great with the HD600 (again just my personal opinion) - and again I'm struck by the fact that the HD600 is a pretty easy load to drive. I even tried using iPhone > digital out > Q1ii >line-out > A5, and there really isn't much (if any improvement). So personally I think (with the HD600 anyway), that the Q1ii output is pretty good - even SE.
I now have a balanced cable for my HD800S - and that was the last test.
First up - SE.
The HD800S sounds pretty good on both - buts its clear in the comparison that the AM3 amp unit on the Q5 has better control on the driver. Bass sounds a little loose with the Q1ii - not awful - there's just a noticeable difference.
Now balanced.
Both Q1ii and Q5 balanced (with this headphone) are an improvement over SE (Q5 with AM3A). In fact the Q1ii balanced sounds pretty darn good. But the Q5 is at a slightly different level. Only disclaimer I have here is that its really hard to volume match the headphones, so I could be slightly out in the volume - and this could cause a false impression.
Overall - I'd say:
With IEMs - assuming you need portability - go with Q1ii
With headphones - it will depend on the impedance and sensitivity - but if its harder to drive, then definitely recommend considering the Q5. Q1ii still does a great job with the HD600 though.
For the HD800S .... balanced .... Q5 => yummy.
Two tracks I tested with : Pink Floyd "Have a Cigar" & Elton John "Bennie and the Jets" (live)