Sennheiser's for the most are NOT warm. But you don't want
all of your headphones to be warm. Variety is the spice of life.
I went through the whole HD6X line, multiple times and found them pretty boring. I am really enjoying the S2'Ss though.
My favourite headphones are the Grado GH2's, Focal Elex's and HiFiman HE6se V2's. The iBasso SR2's and HD660S2's are really working their way to my heart. For closed backs, I really enjoy my Focal Radiance's and CFA Cascades.
So, as you can see, I love warm, fun headphones. And my music choices are new rock, classic rock and horn jazz.
Just an opinion for you.