Well, Zeph has already heard me talk about this. As I have probably mentioned, I play the violin. This isn't actually related, but it gives me a bias. Warning you now.
So anyway, there's this epic string quartet that takes any sort of other music and changes it into a piece for string quartet. It is very epic win. Some of their better stuff includes Muse, Three Days Grace, and Nirvana, but there's a ton of other really good stuff. They did freaking Bohemian Rhapsody. It made me laugh.
This part is mostly for Jaguar. Jag, you need to look this up on youtube. They have a whole tribute album to Disturbed. And yes, they have Voices and Down With The Sickness. I just remembered you liked those.
Everyone else, I forgot they did Through The Fire and Flames by Dragonforce. That is quite possibly their best one. It is epic.
The group is called the Vitamin String Quartet, but there's another one called Apocalyptica which does... Metallica, mostly. I honestly thought they were pretty good, but not as good. Their rendition of Enter Sandman was really good because they perfectly did the guitar solo on a cello.