Well, Apple has not yet seen the Intel chips be cheaper than the PowerPC chips, which is unfortunate. But I imagine that the system runs cooler. Not that that's such a big deal for the Mini, as opposed to the laptops, where it is. I imagine that the move to the Intel chips on the Minis is just a result of being a closely related architecture to the laptops. The additional memory is probably just to hide the additional cost.

That said, I can't imagine anyone having a homebrew home theater PC actually keeping the data on the direct-attached storage on that PC. At the very least, it's difficult to upgrade and back up. You can also easily reach a maximum amount of storage, whereas remote filesystems can be expanded indefinitely. Also, more direct-attached storage means more heat. So I don't see smallish hard drives being a concern. Although, it probably is the largest laptop hard drive available.