I've known about these guys for a couple years now. Their renditions of the Metroid soundtrack have inspired me by their just sheer awesomeness on more than one occasion. Up top is the Boss Medley from the Super Nintendo's "Super Metroid" game. And man it brings back memories in a much more badass way than before.
That one is pretty explainable. It's the theme to Torvus Bog from the Second Game in the Metroid Prime series. Which by the way, if you've never played the Metroid Prime trilogy, I highly suggest you pick it up for the Wii. There is a Collector's Edition(which I own) that's pretty sweet, but they also have just a normal old Prime Trilogy you can buy with all Three games on one disc. Check it out!