PRaT = pacing, rhythm, and timing. It refers to how fast / slow / lively the sound is, Since it refers to speed, I'm not sure how it was being differentiated from "fast," but sometimes reviewers use PRaT to refer to "musicality." Neither term is really clear.
HE400 is a safe choice (and you should be able to increase the padding on the headband). Look at HE300 too; it has some popularity with the Grado crowd, so I would suppose it's also good for metal. Or try SR60i with L-cushions.
I happen to like SRH840 as an all-rounder, but it's closed, it doesn't really stand out with any particular genre, and the headband's uncomfortable. SRH940 is comfortable and resolving, but too bright. The HE400 is a better choice than either. I haven't yet heard SRH1x40.
Since I see that some of the parts for the HE 400 have quality control issues. Example, ear pads, cable, headband etc. I tried looking on amazon to see if i could find after market accessory addons for the HE 400, but I wasn't able to find any. Do you know where I could get accessories?