I have had mine for about 3 months now and drive Talon Raven C's. I have installed two sets of NOS tubes after having listened to the stock tubes. The first, a set of Matsushita 1960 vintage and more recently a set of Amperex 6DJ8's. All 3 sets of tubes sounded just fine, with the Amperex tubes sounding a tad bit more 'open' and detailed. The only problem I have had involved the remote, the down volume button worked sporadically and DK replaced it immediately without complaint. I find the amp plenty powerful and excellent in the bass reproduction. It is relaxed, refined, and smooth through the midrange and extended in the upper frequency response. It is dead quiet and it is musical. I tend to like my music a little louder than the average bear and I tend to judge (at least to some degree) products based on how loud they will let me play them. If I feel like I have to contain the volume, that tells me something does not sound right. The DK sounds good at low volumes, very good at mid volumes and it stays that way till even I can't handle the sound pressure level. For my taste it may be just a tad bit relaxed, but then it is still relatively new and my speakers are new as well. This amp will not wear you out or get on your nerves nor will it put you to sleep. The music sounds natural and realistic. As the volume increases it remains in control and does not go 'over the top'. I purchased a seperate phono stage, but did listen to the phono stage of the DK and it was just fine, nothing to complain about and I could easily have used it, considering I play a lot of vinyl. This amp is dynamic and it is simple to use. I really don't understand all the negative press many have presented regarding this product. I have owned Cary, Alchemist, Electrocompaniet -- all fine products and the DK competes in every sense with them, for less money.