One of the biggest surprises of the past few years is Christian metalcore act Underoath, who've sold almost a million copies of 2004's breakout underground hit, They're Only Chasing Safety, and its gold-selling follow-up, Define the Great Line. Almost as amazing: Their breakthrough was for little Northwestern Christian indie label Tooth & Nail and came after six years of hard touring and frequent lineup changes. A big part of the band's cult-like following is its reputation for writhing, drooling, balls-out performances that blend hardcore's intensity and doom metal's churning, pyrotechnic rumble. Though they were disappointed with the production on Chasing Safety, the cleaner, poppier emo sound undoubtedly garnered them a lot of new fans, who are probably puzzled by the darker, louder Define. The Florida sextet's sharpened the angularities of their sound even as they've polished their songwriting, separating themselves from the pack with epic tracks that marry anguished roar, insistent (if sometimes submerged) melody, dramatic arrangements and flashes of adventurous experimentalism.