I had a Beosystem 2000 from 2003 to 2006 and went to Beosystem 6000/8000 and 6500.
As for CDX I also went for one though I used a portable Philips with the 2000 system and I still got it.
The connections on a Beomaster 2000 are limited in inputs so the tape input is the only option and a CDX is with RCA plugs so you would need a converter plug. I used a Beocord 2000 but it would work best input wise deciding on cd or tape for good.
The CDX is a great sounding not harsh or digital player where the lazer is yet to give known problems. Left hinge and cold solderings but not difficult to get serviced. All CDX reviews gets the thumbs up including me. It would also match a Beomaster 2000 fine in design.
1: A CD3300 would work but designed for the Beomaster 3300 so you would be better of with the CDX. Research on CD3300 here on Beoworld for problems.
2: A CDX is worth the money and the prices go up as it is a great unit. For a Beomaster 2000 it is the most ideal one.
3: To accept an offer for a 6500 system? I did twice so far but after the 2000 it was 6000/8000 first. But different B&O for different needs. I even think my old 2000 system is currently for sale here in Denmark. I have seen the ad. Would I want it back? So far no need.
What are the needs and the desire here? A higher quality built Beosystem and more options such as powerlink and be able to connect to the newest Beovisions coming out these days? Use active or passive speakers? Linking to MCL or Master link? Is it the design? The smaller space it takes? I used an Attyca II B&O stand for the 3 units 2000 and now my white 6500 is using the Attyca I saving good space. What about controlling it with a Beolink 1000/Beo4 or Beolink 7000? A greater Beocord with HX pro? I use 5500 and 6500 and they play/record great. With great Beocords you may develop an interest in cassette tapes.
I like the high quality, design and the options. That is why I got a 6500 these days.