I run all Aesthetix Eclipse gear: Atlas monos, Janus pre and Romulus DAC/transport. Fully upgraded LP12 with Lyra Kleos (please don't bash the Linn) and Raidho TD2.2's. My system is pretty much where I want to be. I rolled tubes in my Aestheix gear for about 18 months before I got what I wanted. Major impact will come from the transformers and caps (mention above). I noticed this when I upgraded my DAC to the eclipse model.
The more resolving your system, (obviously) the more dramatic the effect of different tubes. My experience (guided by the fine people at Aesthetix - Jim and Glenn) was the biggest jump in SQ was in the phono preamp. V1 will have the most impact. I tried PSvane, Treasure, Gold Lions, Tele NOS, and finally found it in Amperex ultra low noise12AX7. Moved the Tele's to V2 and V3 and changed from (6DJ8)6922s to 7308s. For me it was all about low noise floor - which opens up every other sound spectrum IMO.
Changed to Tele 12AX7 NOS and Mullard 7308s in my DAC/CD - which for me really gave it the analog sound I wanted. Based on my experience. I prefer NOS versus new tubes.
Takeaway: get everything else where you want it to be first. including your room acoustics! Identify what you want to improve and check out what Brent Jesse has to offer. His descriptions are good and will help you identify a possible solution at a given price point. Be careful, with NOS tubes, there are a lot of imposters out there.
Make it fun. Enjoy the process. Good luck
