To my ears and body nothing handles the heavy metal genre (as others) like pro drivers, i.e. through compression drivers via horns or waveguides and larger diameter bass/midrange units, preferably in addition with a sub (also with larger diameter, 15"+ units).
My recommendation, also to stay within affordability, would be for the Geddes loudspeaker model Abbey (would have preferred the larger Summa model, but I'm not sure whether they're still made), which are in the need of the assistance of a sub. They're to be had both as DIY and pre-assembled, ranging from $1,700 to $3,000 per piece.
http://www.gedlee.com/loudspeakers.htmThese comprises pro drivers from Italian manufacturer B&C, and what's very important here is how they're able to withstand serious beating without breaking a sweat (many others brands of pro driver would do similarly well), hereby providing that elusive but extremely vital aspect of effortlessness to the sound. Moreover they're able to communicate the edge, energy and sheer feeling of power needed, not only for this genre of music, without in any way sounding harsh.
Many an audiophile would disagree on pro drivers not sounding harsh, but well implemented they'll cleanly give you dynamics (both micro and macro) and transient response that would see most typical hifi-speakers crumble into smoke trying to achieve. Hearing cleanly reproduced dynamics and transients approaching live levels might deceive some into thinking it sounds "harsh," simply for the reason that they've never before heard it via any typical hifi-speaker, which are prone to seriously "mute" and lessen the impact of dynamics.
But remember, it's not so much about max. SPL's per se as that feeling of effortlessness, low distortion, ignition, and the sheer area of displacement afforded by the bigger units and horns/waveguides. Heavy metal needs to be felt as well as heard.