If you get proof of the original purchase with the player (whether direct from SB or from a retailer such as Car Toys or carplayer.com) then you're covered within the terms of the warranty from the original purchase date.

If you can't prove when the player was purchased then you will be pretty much at the mercy of David's good will! Of course if the original purchaser has invalidated the warranty then you inherit that problem as well.

I think that's pretty much what you would expect of any product that you purchased second hand which is still within the manufacturers warranty period (apart from the bit about David).

Rob