I'm thinking the Ultrasone DJ1 or HFI-580 (135ish on Amazon) would be a great set for your j-pop and mainstream music. The bass is fantastic for the price, and since it's a closed-back design, you can use them whenever you require some noise isolation.
For a complimentary set, I'd recommend either the Audio-Technica AD700 (95-ish on Amazon) or Grado SR60/SR80 (79 or 99). Both are open-backed so you'll get a more airy sound. The AD700 will have a laid-back signature and expansive soundstage. The Grados will be engaging and in-your-face with lots of treble and detail.
Just my two cents.
Ha! I own the Alessandro ms1 and am about to get a second hand pair of DJ1 from a friend (who is sadly quitting this hobby slowly). Great minds think alike!