Pink Floyd and Weed

Really enjoying some Pink Floyd, the Division Bell. Hi-Res download from my PC to my DAC. Anyway, listening to my headphones and noticing way less bass than through my main speakers, nothing I can adjust. My headphone playback is through a modified Musical Fidelity Amp going to a set of Sennheiser HD600 phones, is it the headphones or the amp sucking the bass life out of the music?

If necessary, I can replace the headphones or the amp, but not both.

Thanks!