Sennheiser has unveiled six new headsets featuring Apple-compatible in-line remotes and mics. The IE 8i ($600) is an in-ear headphone offering clear, balanced sound, while the MM 70i ($130) are also in-ear headphones, but are designed to offer more pronounced bass. The PX 100-IIi ($120) and PX 200-IIi ($140) on-the-ear headsets are similar, with the open 100-IIi offering more balanced sound than the closed, bass-heavy 200-IIi; the same differences…