I've been looking for a set of headphones for my home
studio. They need to be closed because they'll be
used for monitoring during vocals. They'll also be
used for mixing and monitoring playing on synth
keyboards.

After visiting some local stores with headphone walls,
I've found the AKG K271S and the Beyerdynamic DT770 Pro
both in my price range and sound good. I bought the
DT770 Pro's, but then I heard that they're hard to
drive and I got a little worried, so I didn't unpack
them. They are 250 ohm, compared to 55 ohm for the
K271S. I will mostly use these with a Mackie 1202 VLZ
mixer, or plugged directly into a keyboard synth
(like a Korg Triton Extreme, or a Yamaha Motif ES8, etc.)
Would I be better off returning the DT770 Pro and exchanging
for the K271S?