I would personally change headphones first Yes, HD800 sounds good with Dave but the times of HD800 are a bit over. My Hifimans are on a completely different SQ level...
Re "Music sounds better in the night": Perhaps power-related or mood-related?
Impatiently waiting for my M Scaler. Still not available locally...
Susvara is many times the price though. I will say, no $1,500 headphone is a significant step above the HD 800 in sound quality, for the type of sound presentation it pursues.