Another metalhead here!! I can tell you, as a fun of this music, even though more into Euro-power metal, the Axioms sound awesome for this music. My M60s have all the oomph and crisp that I would require. You will not be wrong with purchasing Axioms.
As for two floorstanders vs. to bookshelves plus a sub for 2 channel music: I was last night at a family friend home, and I was amazed with the quality of his system - two Totem Reference monitors and a sub, simply awesome. However, he had very expensive gear to drive the speakers with: a tube pre amp and a class A Passe power amp, rated only 2X30 watts at 4 Ohms, with external DACs for his dedicated CD player.
