I've ordered Indigo Xtreme (for 1556, though it's the same for 1555 as I understand it) to test out.
The stock paste is alright according to a corsair rep it's Dow Corning Thermal Interface Material. If you must change it out, go with MX-4 or Shin Etsu.
I've ordered Indigo Xtreme (for 1556, though it's the same for 1555 as I understand it) to test out.