The Beresfords, or any DAC with a headphone socket have amps inside them. The concentration will be on the quality of the DAC as opposed to the amp. My X-CANSV8P is a headphone amp with a DAC, where the concentration is on the amp part.
I have not heard the Beresford, but going by other comments, if you are going to be an occasional headphone user and are happy with the SR60s, then I am sure it will be fine. SpiceWeasel, the jump to the SR80is is about £20 more if you shop around and to me, I dont understand why they don't get the awards the SR60is do. Try and audition them.
The SQ from standard to premium Spotify is not huge, but add in the advantages of being able to download music to your PC and no adverts make it very worthwhile IMHO. Just remember to edit - preferences and then tick the enable higher bit rate box in sounds