Steve, I have a Beosystem 6500 which I'm controlling with a Beo4, because it is connected to a BeoVision 8 and a BeoLab 2000. The integration to the BV8 made using a Beo4 the easiest choice, though I have both a Beolink 5000 and an MCP6500. Before getting the BV8, I used the Beolink 5000 for day-to-day operation.
If you want to control it with the Beo4, you should know there are various versions, and you'd really want to look for a Beo4 which has PHONO in the LIST selections. My Beo4 does not, and I have to use N.RADIO to start the record player - which, if I'd had N.RADIO functionality in that system wouldn't have been so smart.
Apart from that, using the Beo4 is no problem at all, and while I can be very critical of B&O at times, I am simply amazed at how well these units work together. I can sit in the kitchen and get the BBC News sound through the BeoLab 2000, routed from the BV8/STB through the Beosystem 6500 to me. Or I can go into the home office and enjoy the sheer beauty of a BV8 and a Beosystem 6500 together, as well as the excellent sound.
I do use the MCP6500 to do TIMER programming of the Beosystem 6500, something I doubt you can do with the Beo4, haven't even tried.
(And yes - there's a mint condition Beolink 7000, with the charging stand, for sale locally. Have been tempted.)