I've been profiling post rock bands for the past few weeks because I think post rock has a lot in common with New Age music, even though the audiences for the two genres are probably completely distinct. Both styles of music are largely instrumental, both use wandering rhythms with no set time signatures, both are seemingly structureless, both are highly introspective in nature and both tend to induce a calm and meditative frame of mind.
The two biggest differences, other than cultural, are these- post-rock uses rock instruments such as electric guitars and New Age music generally doesn't, and New Age music is almost always positive and optimistic in emotional tone. Post rock tends to explore a wider range of emotions and moods.
Personally, I think this is a good thing. To the extent that New Age music has a spiritual aspect to it, I question the depth of any spirituality that requires constant optimism and positivity in a world such as this one. By delving into emotions of sorrow, anger or fear as well as joy and beauty, post rock may actually play a more effective role as an aid to meditation than New Age music.