I am looking to replace my JVC Marshmellows so I am certain whatever earphone I purchase will be a decent upgrade.
To help receive the best suggestion for the earphones, here is the order from greatest to least of the kind of genres of music that I listen to the most:
Acoustical Rock(ala John Mayer, Jack Johnson)/Alternative rock(Linkin Park, 311, Weezer, U2, Coldplay...)/Soul(Stevie Wonder, Al Green, Earth Wind n Fire, Bill Withers)/Blues(Michael Buble, Norah Jones, Colbie Caillat)/Rock(Hall & Oates, John Lennon, Eagles, Goo Goo Dolls, Red Hot Chili Peppers) /RnB(John Legend, Musiq Soulchild, Maxwell, D'Angelo, Boyz II Men)/Rap(A Tribe Called Quest, Q-Tip, Common, Lupe Fiasco, N.E.R.D)/Electronical(Daft Punk, Gorillaz)/Hip-Hop(Outcast, Eminem, Kanye West)
Some of the artist/bands that I have sorted for each genre may not be accurate, but I am sure it can give you a good idea.
Superior soundstage to most any IEM I have heard
Cloth sheathed cable
My first good headphone, got me into headfi. After I lost the PortaPro, it took me the purchase and return of 5 other headphones to find something better. Most of the others where $100 or more, like the Etymotic Hf5, the Koss, CC_01, Audio Technica AD700, Zaggphones, and finally a superior dual element Koss KDE/250.
Bass is clear on the PortaPro, and the treble maintains it's sparkle. Excellent decay on drums and percussion (the note fades in the correct amount of time) makes for a satisfying listen if you like bass and drums.
M9 really shouldn't cost you more than $20... for $30-40 you can get an M6.
I wouldn't recommend the RE2 for your genres. They work great with classical and vocal-based genres but I'd really want more extension for hip-hop and electronica. The UHP336 is also one I don't like due to usability issues (it's a 4-year-old design, after all).
For $40 my choice would be a ViSang R02 (ebay) or Brainwavz M1 (mp4nation.net - currently out of stock). Both sound much much better than the price indicates. The R02 is a bit more bassy, the M1 is a little more trebl-y, but the core signature is very similar.