In The Nightside Eclipse is a spotless 10/10, it has an atmosphere which I doubt even the members could control when writing it, it's something which just happens on a subconscious level.
I have never gotten into Anthems To The Welkin At Dust, and I probably never will. To me it always feels like a forced Nightside, as if they wanted to sound the same, but instead of the music coming naturally, they pushed everything in there and just made a disjointed mess of it.
IX Equilibrium and Prometheus I like. They're nowhere near Nightside of course, but unlike Anthems they stand on their own legs as interesting quirky, albeit a bit random, albums. They're very hit and miss, but both are worth getting yourself into if you have some spare time on your hands.