Please note that the Soundbridge has its limitations itself!
There is only a limited memory in the SBs, so they cannot load an indefinitely big playlists. That is however often not the limiting factor. The SBs also have a timeout and the longer the list the more time it needs.
Up to about 10k songs one finds usually success report. When you exceed that you need to use some tricks like indexing the database, using sqlite3 database over sqlite2 etc. There are forum posts about it.
And at some point it simply wont be fast enough any more and the timeout occurs – cannot load.
For 9k songs I would try to optimize the DL speed a bit and that should be doable.