If it really has to be the Sport (which I appreciate for its sound quality) and you can renounce database involvement, there’s the Sport’s folder mode allowing access to all songs without a file-number limitation.
If you like shuffle play, there’s no other «clean» solution than putting your whole collection in a playlist, preferrably with all songs on the card, as a directory mix doesn’t seem to work reliably (it does with one of my cards, but not with the other…). There may be a song limitation somewhere above 5000, though.
In one of my two Sports I have a 64 GB card with all (>6000) songs straight in the «Music» folder to enable shuffle play through folder mode. This solution does work, but makes the player slow.
