The endosymbiotic theory suggests that mitochondria are--or at least were--a separate species themselves. That they developed from bacteria co-opted by other cells as power plants, eventually becoming the stripped-down symbionts we know today. It would explain why they have their own DNA, and I'd say it would make them (mostly) irrelevant to determination of the species they inhabit.
I was happy with http://www.rjtech.com/. They offer a lot of customization options on top of their bare bones laptops, and I found their service excellent. They're not cheap, but they've got some very nice kit, and I didn't have to give MS money for an OS I didn't want.