I put my M-100 on eBay too. Looking for a more balanced headphone, I want to get the NAD hp50. I think they'll also work as a more relaxed home headphones.
Would love to keep the M-100 too...
I find the m-100 a little bassy too but after I tried reducing the bass with EQ it sounded more natural, similar to the XS, but still retain its warm and dark tone.
How is the sellers feedback looking? Study the comments, look at the dates (i.e. continuously active etc.), look what else he is/was selling... ask questions and look at the overall tone of the reply.
Furthermore: what das 'seller refurbished' mean? What did he do with them? Replace parts? With what? Offizial Dealer of maybe in V-Modas blacklist?
If something sounds too good to be true... it normally is ;-)
Listening to Booka Shade's album from last year 'Eve' on M100 atm at work with E17. I've listened to this album quite a few times, mostly on TH600 but I think I listened once with M100s + xl pads. The bass is impressive with stock pads. Some crazy quantity and pressure on some tracks, verging on skull rattling but nice and clean.
This track particularly stood out (bass drop @ just after 2 minutes in ) but the whole album is extremely well produced and full of great bass lines.