I haven't actively listened to Clutch in a few years, but if you want REAL pure rock fury, I would pick up their first full-length, Transnational Speedway League: Anthems, Anecdotes & Undeniable Truths. The first track, A Shogun Named Marcus, is one of the hardest rock songs I've ever heard. Their second album is pretty great, too (and has Escape from the Prison Planet on it).