My PMx2s are getting signs of battered use (usually cosmetics).
However, are there any current offerings that rivals these especially where it excells (ie Timbre, Neutrality and Freq. Response smoothness)?
Yes, definitely, but expensive. Meze Empyrean are very close and IMO somewhat better. Both are lovely sounding, highly enjoyable.
Here's my view of the differences, it's an opinion, other views may differ somewhat.
Empyrean has slightly more detail, a touch more transparency.
PMx2 has a slightly fuller midrange.
Empyrean has slightly more bass, and it's well defined bass. Don't take this wrong, I don't mean PMX2 isn't well defined.
I'd say these differences are small, but there. Which is more correct? Hard to say; the PMx2 is superb for vocals, with great naturalness, tone, and perhaps a touch of warmth; the Empyrean might be a touch more neutral, and with the fine transparency (without harshness!) gives superb realism. Both superb but with very slightly different flavours; I now prefer the Empyrean.
Both are very comfortable, the PMx2 slightly more so.
Though figures for sensitivity are similar and people say the Empyrean is easy to drive, I find the Empyrean a bit less sensitive, and it benefits from some power to get the best out of them.
Obviously all phones benefit from a good source and amp, but this seems particularly true of the Empyrean. They love a good valve amp, but I've had to develop my DIY valve amp to get really good results.
With a superb Lector R2R/valve dac and a decent valve amp, the Empyrean gives plenty of fine, spine-tingly music; close to musical heaven.
Timbre, neutrality, response smoothness - yes, Empyrean does all these exceptionally well, but add 'enjoyment' to the list.
Plenty of info on the thread here.