Sigur Rós are an interesting case. They are one of my favourite bands. Their music is often called post-rock, which may or may not be accurate. At least some characteristics of their tunes are long songs, epic atmospheres and emotional vocals (often not in any language).
I'd like to think that all of those things would benefit from larger dynamic range than pop or rock.
But no. Take a look at Sigur Rós releases in theDR database. Their first album [i[Von has the largest dynamic range; it's all in all rather different from the later ones. The later releases have DR of 7-9. Even though one of the best albums of all time, ( ), has the largest one at 9, it's barely enough: for example, Untitled 8 ([Popplagið]) would sound so much more epic with greater dynamics and a soaring climax.
Incidentally, such versions can be found on bootleg live recordings, which are often of good quality. I find I listen to the official releases less often than bootlegs. Oh,this goes especially for songs on Ágætis Byrjun and Takk...
I think there are many disappointments. From some data available at the dr database: Godspeed You! Black Emperor -- mostly loud Mogwai -- compare the original Young Team and the remaster Explosions in the Sky -- not so different
Older band Talk Talk is noticeably less loud (but I haven't yet fallen for Talk Talk).
Sigur Rós: Epic and (almost) too loud