are both of your ext hds self powered. or is any of them being pwered from ps3 usbs. if thats not the problem , only solution would be to buy a 1.5tb hd (tescos £79) or why do you need both hds connected, use 1 drive for games from A to M and another for games N to Z and then its easy to know which one to connect.
i've got 74 games on a 1tb hd and still got 340gigs of space, the hardrive also has a folder with all my important ps3 files on it. why could you possibly need 2 harddrives connected. thats an awfull lot of games, you cant possibly play them all. put all the ones you hardly play on one drive, and the rest on the other.