The Beosat RX is a stand alone sat receiver. What you are talking about, is a LM Sat controller built inside a LX5500 or MX5500/6000/7000.
And yes, i still use the LM Sat with an MX5500 every day, it works great and there a still 35 analog german channels, more than enough :)
The Beosat RX is still not useless, it can be modified. Originally it uses 2 antenna wires, a horizontal and vertical wire. But it can be modified to a single wire system, 14/18V switch for H/V switching. I use ist still on a MX5000, the only thing is, it has only 32 channels memory.
And: both can be expanded with a digital receiver, using a special cable. The Beosat works then as a third AV-Port.