i was in your spot a few months back. i currently have HE-500, T1, HD 800, and LCD-2.
i feel like the HE-500 do complement the T1, but they are very similar sounding in some ways. the HE-500 has more midbass, slightly less sub-bass, and is smoother on the treble (with pleathers). with velours, its very similar sounding but the HE-500 is smoother in the treble and mids. that ortho sound. the HE-500 is much more forgiving of poor recordings than the beyers and are really good all rounders. however, ultimately, i feel like the T1 are a better headphone. they are more detailed and have more air and soundstage/imaging, more sub-bass presence, the HE-500 are flatter sounding as well. however, the HE-500 have a slightly better midrange i think, even if its not as detailed or spacious, and the treble is smoother, the bass is punchier. just depends on what you want.
their sound signature is similar, yet also different. basically i feel like the HE-500 is a more forgiving version of the T1. both are great all rounders. (i found that with velours its literally a more forgiving sounding T1, the sound is EXTREMELY similar. velours can sound awkward at times, but they're also very smooth, and great for vocals, electronic music, and pop).
also, the T1 are much more comfortable than the HE-500.
note: i probably would of sold the HE-500 if they weren't so amazing at being forgiving of mainstream music as well as being some of the best headphones for drum and bass, vocal trance, and house music. (they're great, but its hard to justify when you have T1/HD800 as well).
Edited by Dubstep Girl - 5/1/13 at 2:39pm