I have purchased a pair of AKG K702s and am currently driving them with a fiio e5. The Fiio just isnt powerful enough to drive the AKG's and the headphones are so detailed they reveal every struggling breath the amplifier takes. So I went on to something more serious, got a little dot mk3 from ebay, secondhand of course...after buying those headphones dont have much left over. Neway, I was wondering if you can suggest any tubes which would give me better bass, I want more bass without sacrificing the rest of the audio spectrum. The 702s are brilliant if you are wondering, but I really do miss a bit of bass. PLEASE HELP!