With FOX having two singing competition shows on the air now to balance their schedule, NBC unexpectedly found themselves able to mirror that winning formula. With 'The Voice' waiting in the wings for a 2012 return, the network debuted an expanded third season of 'The Sing-Off' (Mon., 8PM ET on NBC).

With its emphasis on a cappella singing groups, 'The Sing-Off' manages to stand separate from its competition in bringing us vocal performances you simply can't see on any other show. Even 'The X Factor' with its group performances doesn't seem likely to get as involved as some of these groups do.

Delilah was a perfect example of how brilliant an a cappella performance can be, blowing us away with their take on Bruno Mars' 'Grenade.' With killer lead vocals backed by innovative harmonies and a variety of beatboxing to round out the musical experience, it was a unique and mesmerizing rendition.

Who are your early favorites on this new season of 'The Sing-Off'?