Great, just when this thread had cooled down I now have time to post
I did this modification (removed the four caps) on my Beomaster 6500 some months ago (as I posted, and got away with surprisingly little general interest). I find the above commentary from a B&O tech ("no influence on sound") a little odd, since even me with my wooden ears and the half an hour or so between before-after could notice the change immediately. Of course the right way to compare would be to do one channel at a time, but I couldn't be bothered. Well, maybe it didn't have much effect when all the rest of the machine was new and all components performing to factory specs. It would be interesting to simulate it, but I believe the circuit is far too complex for PSpice or similar to get any results that are comparable to real world regarding these caps.
Since Beomaster 5000's and many of 5500's have managed to survive without these caps, I don't believe that they are that critical for normal operation. I would expect them to prevent stability problems when the load of the power amps gets funky, i.e with very long speaker cables, or multiroom setups with passive speakers.
Nevertheless, I plan to improve the preamp stages sometime later, and I will probably put these power amp caps back, just smaller in value.