I've experimented with various tubes in the X10D connected to a Radio Shack Optimus 3400 portable CD player in a bedroom system. Even with the stock tubes, the improvements with the X10D are evident, especially in soundstaging. "Better" tubes will improve the sound of the X10D, its just a matter of how much money you want to put in this type of unit. Maybe Kevin at Upscale Audio can make a good recommendation for you. BTW, we experimented with the X10D in a friend's system using a Rega Planet with ARC gear. Although the X10D introduced a slight loss of focus and detail, the large improvements in soundstaging resulted in him keeping the X10D in the system.
Replacement tubes for MF X10-D??
I've read that the X10-D can be improved by replacing the stock tubes. My problem is that I don't remember where I read it. Does anyone have experience with this, or know where I might find out more information??