I'm pleased to report that I have accomplished the revision of the units today. They are running in right now but they do sound very promising. Got the kit from http://www.dadaelectronics.eu (this is no shill, i can proove it with pics :D ). I know there is also kit from http://www.net-audio.co.uk ... The capacitors of the 306 where starting to leak, so I guess it was time for a revision. The opamps of the 34 where swapped out for the newer ones. But don't ask me for any technical details. All I know how to solder the capacitors in the right way
I will compare the Quads directly to the AP30 and see if they have gained in detail. In my initial comparison the AP30 beat the pants off the Quads in terms of clarity and detail... but lets see in a couple of days if the revision has made a "objective" difference.