Trelja: very good question and Ehider gave excellent answer. I will allow to ellaborate here,briefly describing Stan Warren credentials: Hi is "S" in PS Audio and Paul Mcgowen is the "P". Lately, Stan choose to modify other units rather to manufacter his own. (He, of course can build pre/power amp speakers). I love tube equipment. Two non-tube amps are as good as tubes, in my personal limited opinion. One is digital amp Bel Canto EV0 (a bit lean) and... ADCOM modified by Stan, It has - no signature of transistors at all. Price: $250 for 2-3 months labor? There is no guarantee that it will bring him new customers, and also there is long waiting list. I waited 6-7 weeks before Stan could looked into my 9000es. Well, now results: I have 9000es for about a week, sound changes every day. However, even today, I can state its the best CD sound I ever had in my life ( comparison with CEC TL1 Transport, Timbre Technology jitter reduction box and DAC, Electraglide digital cords). In SACD mode its easy outperforms Sony 777es I had before. I am extremely thankful to Stan. In general, if your "modifier" knoes ehat he is doing bying enexpensive electronics and modifying its power supplies and analog stage is the best cost-effective way to improve your system. Good luck. Simon