well after combining my new roommate's collection with mine, we've got a total of 14,864 tracks...
The server was able to get through the indexing of all the tracks with no problem, but the receivers have the reboot problem (if you try to play all tracks). We're still able to go into an artist and play all the tracks within an artist though (haven't gotten around to creating playlists yet).
So looks like you've got a bit of room to grow
You might want to check your ID3 tags to see if there's any odd characters, I think there was a post from someone that said odd characters could cause problems. (not sure what they meant by odd characters, but I'm guessing anything outside normal printable characters (i.e. the graphics chars over ASCII 127 or the control chars under ASCII 32 but that's just a guess)
(By the way, the server software will die on indexing somewhere less than 33,000 tracks, first day I got the receiver I just had to try it out right away and forgot to limit the search paths)
~fiddy