Do you mean Sennheiser HD 800s? I have the HD 800 (not the "s" model) and Hifiman HE 560. I have not heard the Sundara, but if it has the Hifiman "house" sound, it's a very different animal than the HD 800. The HD 800 is a very revealing headphone and some consider it "bright" (I don't). From what I've read, the HD 800s tones things down a bit. The Hifiman is a much "warmer" sound.
Saying anything is the "best" is always subjective, but for under $1K my recommendation would be the Focal Elex from drop.com.
https://drop.com/buy/massdrop-x-focal-elex-headphones
Saying anything is the "best" is always subjective, but for under $1K my recommendation would be the Focal Elex from drop.com.
https://drop.com/buy/massdrop-x-focal-elex-headphones