Ah, okay. Well, it not like I can help a ton more, but for your use, it seems to me that whatever in the tower should be fine when you get it (except for RAM; I'll repeat the general mantra, more is better) - I don't know about OSX and playing DRM media, though. AND ANOTHER THING! It shouldn't really matter, but HDMI is basically DVI with an audio channel. If you intend on running another monitor (besides your television) at a higher rez then 1900x1080, you may have to worry about which DVI port is single-link and which is dual-link. HDMI is single link (I think), but anything higher requires dual-link.
I THINK! Can somebody affirm me on this?
Anyways, for your second drive, since you aren't worried about RAID, research on your hard drives to find a big one with a good write speed.