I have a similiar question, i've got the same D, K and BK versions as the OP and would like to buy a game from XBOX Live. I have a maybe 2-3 month old ixtreme version flashed, cant remember exactly which one.
i sold almost all my xbox games, so i dont care for backups atm, cause i dont have any.
could i just update to newest dash, buy limbo in xbox live, and then flash my drive later on when i actually have backups i want to ply?
thanks, and sorry for hijacking the thread