I don't know how an IEM can be both warmer and brighter than the M2, aren't those sort of the opposite? Unless you're looking for a V-shaped sound signature, which is what the TF10 has. Brainwavz B2's or the DBA-02's are a good upgrade if you want to go the analytical route. They're definitely brighter and have more detail and clarity but aren't particularly bassy. The GR07 is another very good choice, which is neutral with a slight focus on the bass.
2/1/12 at 9:30pm