I have tried Solens, Mundorf Silvers, Hovlands, Theta Audio Caps and Auricaps and Cardas caps in the x/o. By far the best are the Cardas caps which allow a seamless, unforced and supremely balanced sound. The highly touted oil-filled Mundorfs had a harsh, grainy sound that superficially sounded lively in the characteristic Solen Fashion. The Theta AudioCaps are slightly smoother yet less detailed. The Auricaps have a creamy deep midrange but compress dynamics and sound too rolled off at the HF.