Slashdot has links to a pair of reviews for (compatible) modifications that let you fit an extra 2 and 3 hard drives inside your G5 Mac — install both for five additional drives giving you space for a total of seven drives. Heat does not appear to be an issue, neither does power. It seems like overkill, but a little while ago I thought that external devices were the way to go until I ran out of power points. Not to mention the cost overhead of external cases. If only my PC case was as well designed as a Mac I might be able to fit seven hard drives in there without them overheating.