Obscure music, hmmm...?
I don't know what kind of music you're looking for but I'd definitely recommend GYBE as an experimentalist band (though they're not really obscure anymore). I haven't heard much Sigur Ros, but I'm kind of turned off by the whole idea of Hopelandic — how cheesy and pretentious can you get? I also haven't heard any Mogwai, but I hear they're quite good if you like GYBE, and I might check them out soon. If you're looking for something with both experimentalism and a bit of mainstream appeal, I live off of artists like Porcupine Tree, Devin Townsend/Strapping Young Lad (for a more metal flavor), the Gathering (self-dubbed "trip-rock" for their combination of gothic metal, pop w/ female vocals and trip hop) and sometimes, just sometimes, Opeth...especially their latest album, Damnation.
-Derrick