Trying to decide between the Vali+Modi combo or O2+ODAC for the 650's. New here. Suggestions?

Hi guys, first post here. I recently bought the HD650's and currently own a FiiO E18. I'm looking to get a little more out of my headphones and was wondering which amp/dac would compliment the HD650's better . I've done quite a bit of research and a lot of people have suggested the Bottlehead...