When you say METAL, you mean distortion and overdrive?
As far as versatile for a headphone amp, I think it is a choice between Clean with the drive or gain down, and then the range you can get as you up those?
so If you are to rely on the clean settings, they are all three quality units.
Starting with price, this one goes up against the Ampeg.
Both nice units, both probably have good clean and driven sound.
The BIG stand out advantage to the Elements is that it is more of a portable, go anywhere option, and just the ergonomics of the device make it an easier to deal with unit, and looks sleek as well.
Honestly I can not say which would be the best for clean tones, I am not sure any one of the three would stand out clean, but I could be dead wrong about that.
Hopefully some of the experts on these devices chime in.