I can only speak to my experience with my Golden Atlantic TRP3. The TRP stands for “Tube Rollers Paradise” and the dacs will work with a large variety of tubes (both pentodes and indirectly heated triodes). While there are some pentodes I enjoy I have to say that I much prefer triodes overall for their linearity and output.
Tubes can expensive really fast but (as with anything) it depends upon what you’re looking for. I own two tube dacs and I never roll tubes in the other one (Aqua La Scala MKII). It’s not because I can’t but rather it’s more trouble than it’s worth.
The TRP is all about tailoring the sound quality to your system- and the tubes you use will have the most influence in this regard. There are MANY tubes available that do not require breaking the bank- it just requires a little diligence and patience as how they work within your system requires a learning curve.
If you’re interested in learning more about it I would suggest searching out the TRP tube rolling thread at what’s best forum. I, and others I communicate with regularly post our experiences there.