So Amazon says you can't use the Core system (no HDD), the Arcade System (memory card), or the 4 GB slim (no HDD) but doesn't say anything about the original 20 GB consoles. If it requires 20 gigs then that console won't work. If I can augment it with a USB drive it will. What's the answer? I've had this game pre-ordered for ages and I'd hate to have to cancel it because Bungie decided to alienate a quarter of it's market base.