I own two of the TU-8200 dx. The first one I upgraded several capacitors, but couldn't tell any difference. The second I got has Lundhahl transformers. I love them both and use them for my Recording studio to drive small studio monitors and my mastering headphones. I love these amps. To be honest I really can't tell a difference between the stock output transformers and the Lundahl. I also have upgraded the tubes in one to vintage RCA 6L6 and clear top RCA 12au7. Again, I can't tell the difference between those and the stock EH tubes.
I have multiple vintage tube amps...several upgraded Dynaco ST-70, and several Heathkits (W5M, AA10, and UA-2), all with upgraded capacitors. Again, the TU-8200 beats them all for ease of use, and sound. Plus, it operates at multiple input voltages (you have to re-solder). Love these!