I just remember Chris Coaster saying when he was trying to put together some .2mm upgrade kits, that the transformer used in the .2mm version was larger and he was trying to source replacements.

Having worked on a couple of 568's, I've not noticed any differences in transformer size, although there is a mention of a transformer swap in the upgrade notes.

With regards to firmware - 2.5b9 is very close in sound to the 861, and if you don't use Trifield, is probably the best bet.

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200.2HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5200HC, DSP33
Spare: MCD, 100 Series, 200 Series, 500 Series, F80s, C15s.