I own one, and two friends own them as well. We are all owners of Modwright Sony 999ES Signature Platinum edition DVD players. The tube rectified power supply is a significant upgrade. More natural sound with less grain than the solid state power supply.
I have replaced the stock Sovtek 5AR4 with a Mullard Blackburn, UK 5AR4 from the mid 1960s. Tighter, more coherent sound through my Modwright Sony 999ES with the vintage Mullard. I have no experience using the Mullard 5AR4 in the Modwright Sony 9100ES or Modwright preamp.
I have replaced the stock Sovtek 5AR4 with a Mullard Blackburn, UK 5AR4 from the mid 1960s. Tighter, more coherent sound through my Modwright Sony 999ES with the vintage Mullard. I have no experience using the Mullard 5AR4 in the Modwright Sony 9100ES or Modwright preamp.

