i use this kind of "layering" - as you call it - also inmy songwriting. Basically i come up with a cool melody/riff and i build up a rythm part underneath which is either pure chords (mostly triads spread on a spectrum of various instruments like strings, winds, piano, etc) plus part of those triads (mostly the powerchords) for the rythm guitars, or some rythmic chord-riffing-doublepick-whatever. my songs are more like counterpointed arrangements - i think thats what pleases you when you talk about "layering"

here are a few bands who use heaps of that stuff:

BlindGuardian
GammaRay
Therion
Haggard
Rhapsody
etc.