Anybody with 2,000 CDs wouldn't be called a collector, but a horder. A collector is picky about what he owns and doesn't simply keep every disappointment that passes through his hands. 2,000 CDs is unsightly, unsensible, and physically impossible to appreciate.
I don't think that's necessarily the case. I have about 1,000 CD's, and I have full command over them. Sure, there are some I rarely, if ever, listen too, but most of them I have heard many times over. My taste in music is fairly narrow: a lot of classical, quite some Jazz, Rock, and a handful of less common things. But they are all quite standard CD's, like the "greatest hits" collections or main CD's of various groups. Now, if I started to listen more to Opera and chamber music, I would probably have to add another 1,000 to just have the standard works. If I went into depth with Jazz, that would make another 1,000. I have no Rap, little New Age, no Country, no Chrisitian Rock, no Hip-Hop, little Blues, little Folk, little Gospel, little Latin, little soundtracks, and few World Music. That would easily make another 2,000 just to cover basic grounds. I don't think 2,000 is an unreasonable number at all.