[Currawong]

  So I am very happy to go for the Schiit Vali 2 & buy this set of tubes (ECC88 6DJ8) with it. According to this review that I found here on head-fi, those should sound warm & relaxed. Which is what I prefer. I think.. I haven't had much experience just yet with tubes. Are that the correct tubes? I am new to the whole tube world, so.. would need some help or guidance here as well.    
Then I can just pair it with the Modi 2 and be all set? 
 
I know that I mentioned my Sennheiser as my main headphones, but I am almost certain now that my Beyerdynamics DT770 Pro's may actually get a nice boost in quality as well. 
 

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Thank you all so much for providing me with all the information, greatly appreciated!

 
Yup, anything from the 6DJ8 / 6922 / ECC88 / E88CC / CV2492 family.  Buying a pair is a good plan, as if in the future you decide to get one of the bigger amps, you'll have a pair you can use with it.

 

[Kiwiandapple]

   
Yup, anything from the 6DJ8 / 6922 / ECC88 / E88CC / CV2492 family.  Buying a pair is a good plan, as if in the future you decide to get one of the bigger amps, you'll have a pair you can use with it.

 
Ordered the Vali 2 & Modi 2 Uber! Freaking stoked for this, I will get the tubes later. But got them bookmarked, so I'll absolutely get them when-ever I want to experiment with it. It can get fairly pricey - quickly.. but the ones that I found seem very reasonably priced. 
 
I can't thank you enough for providing me with all the information that I really needed. 

 

[cdm116]

You could look into a matched pair of the little dot tubes 6j1p-ev (6zh1p ef95). Can pick them up for about $3.50 on ebay - I've heard good things.