Thanks everybody for some really useful input. A few more questions, if I may:

1 How much would a Beogram 6000 and Beomaster 6000 in near mint condition be likely to cost these days? Are these items very difficult to obtain?

2 I'm presuming that since the Beomaster 6000 has its own remote control, it and the turntable cannot be configured to operate via the Beo 4 or Beo 5? Is its own remote control ultrasound, and does it need to be in line of sight of the equipment?

3  Is the Beomaster 6000 stackable (i.e. could I place the turntable on top of it)? I'm a little pressed for space in that corner of the sitting room, and presently have my Beogram 5500 sitting on top of the Beomaster 5500.

4 If I bought some quadraphonic records now and played them using my MMC2, whilst hunting around for a quad turntable and amp, would this damage the rear channels? 

1. Very rare to find a mint one. And therefore expensive. A lot of these stopped working years ago and were beyond economic repair. Those that are around tend to be cherished - Lee now looks after mine!

2. Ultrasound remote I am afraid - the first B&O one. It does need to be in line of sight . 

3. No! You can't have seen one! The controls are all on the top as is the display. Also not wide enough to put the Beogram on even if you wanted to! The top is perspex so will scratch easily so you wouldn't want to put anything on top anyway.

4. The MMC2 would not damage the records any more than they were already damaged.

You could wall mount the 6000 - though it would take a little ingenuity.  I would get a 3400 if you were really keen on this idea. Lee certainly has one and could be persuaded to part with it. It actually has a better amplifier than the 6000 though is not remote control.

Through the 3400, very similar. I would possibly say better as the amplifier in the 5500 is not the very best - however it is a very convenient device - I use one all the time! The 6000 is not quite as good but I would be hard pressed to tell the difference.

This Beomaster 6000 just appeared on Ebay (USA), and has a while to go, but might be worth watching:

Unfortunately, for some reason on my MacBook, the link option is unavailable, but here is the link for copy/pasting anyway:

http://cgi.ebay.com/Bang-Olufsen-B-O-Beomaster-6000-Tuner-amplifier_W0QQitemZ160260848699QQihZ006QQcategoryZ39783QQssPageNameZWDVWQQrdZ1QQcmdZViewItem 

link😕

Andy T.