Linear power supply for Weiss DAC 204

The LHY power supply is hooked up to the Lumin U2 mini and I would say that I hear a 20% difference. The noise floor was reduced which in turn allowed the mini to sound better than with the original equipment. The change over was not simple so my dealer took care of it.  I use the s booster linear power supply for my Chord Qutest Dac and the improvement in sound quality also about 20%. The S booster was and add on and was easier to install. I should add both products are quality.I purchased the S Booster from Upscale Audio and the LHY from Vinshine Audio. I have had both products for about 6 months.

Can't speak about the U2, only the U2 mini, or your 40% rule. It really depends how resolving your system is. If your system is highly resolving then I believe you will hear a difference with a linear power supply. The linear power supply reduced the noise floor and in turn allow you to hear more of the music. I updated the U2 mini with the LHY power supply.  From what I have read the U2 costs substantially more than the U2 mini. I would not expect that the addition of a linear power supply to the U2 mini will get you close to the performance of the U2.  I am personally waiting for the next network transport to come out replacing the U2 mini.