Well, after around 10 days non-stop operation from receipt of the 2 x Etherregens, which had stabilised and become more relaxed and with greater texture in voices, I tried going back to the 2 x PD Catalyst 2960 switches.
As soon as I installed the Etherregens I recognised they were quieter and timed well, but had various reservations as they burnt in initially. They were encouraging, but didnāt wow me.
So going back to the Ciscos was a bit of a shock. The Etherregens are that much better in my system.
Itās not really a question of soundstage, although this is both wider, deeper and more composed in an unobtrusive ānaturalā way, nor of noise floor, which is much lower, increasing clarity. Nor is it just a question of detail, although there is more across the board. Whatās really impressing me is that all of this is presented in an integrated, unforced way. Which brings me to the above all: the thing really excels in textural detail and subtle timing variations and interplay, doing a fantastically moving job of conveying the interpretative spirit of my favourite performances.
Double bass and cello textural detail is outstanding. Vocal textures are wonderful. Piano is, well, piano⦠from growling percussion to bell and all the rest. And itās not just hammer and strings. I finally feel my digital connections are doing the ND555 justice.
So I like them 
On the pratting around front I also came to the following conclusions (none difficult to reach):
1 Etherregen sounds better than 2 Ciscos and also better than 1 Cisco + Etherregen
2 Etherregens sound better than one. The difference is not as big as moving from 1 Cisco to 2 Ciscos, although the effect in terms of composure, delicacy, texture, noise floor, timing, space and soundstage is not dissimilar. Interestingly, there is, however, very little difference if you connect from the A side of the first Etherregen to the second Etherregen, testifying to the effectiveness of the design. Connect from the B side (as recommended).
I also found that things worked better with the Nucleus connected to the 1st switch as with the dual Ciscos, though the improvement was less marked (again testifying to the design of the Etherregen).
In conclusion, I certainly recommend people try this Etherregen. Buying two is a bit over the top, but worth it for me. Iāll be getting a Sean Jacobs power supply for them as soon as he can find the time to make one for me.
On the cable front, I still prefer the DesignaCable bonded Belden CatSnake Cat5e in my system. The BJC Cat6a have a lower noise floor and more prominent treble detail, but less texture and a less integrated sound.
Iāve got Adam at DesignaCable to make me up some cables using Belden Cat6a CatSnake which differ from the BJC in not being bonded, having stranded rather than solid conductors and having the CatSnake sheaths. Iām hoping these give me a combination of what I like in both the above cables. The new ones will effectively be the same as the Ghent Audio Ethernet cables only not with the Metz RJ45 plugs, which I find irritating and have a known issue plugging into the Roon Nucleus. Theyāll be arriving in a few days, then I can finally stop faffing. Roll on 2020!