Bigkidz, I had sort of a similar issue with my Vk-500 amp, while the bass was great, and it sounded quite good at lower to moderate levels, when the going got rough...like during complex passages at moderate to higher volume...well, dynamics (especially the midrange) seemed a bit constrained. Since the power supply was more than adequate, I always suspected the mosfet output, but I am really not qualified to even speculate on something like that. Have not had a similar issue with my DNA-500. Anyway, that is one reason I did not look harder at the BAT models, along with the suspected HF rolloff some previous BAT owners have mentioned. I did go ahead and purchase a SF Line 2SE. I thought hard about the Line 3, but didn't want to have to worry about 12 tubes, and would not have been able to swing the SE upgrade right away. KR didn't seem to find too much difference between Line 2&3, except maybe the bass and a little in the HF. I am hoping the better parts in the SE version will help with any HF issues, and will allow more bloom in the mids. I would welcome any suggestions for best tubes to use with this unit, and where to get them. Thanks again to all who responded, you provided good suggestions, but I had to start somewhere. Also, the 270 ohm output of the Line 2 is lower than many tube units, and should be low enough to mate well with the (sort of low) 10k ohm input of the DNA-500 (at least it is greater than the 10:1 rule of thumb).