So I bought the Willsenton R-800i

@chmaiwald , GREAT write up. Thank you very much.  I know everything is system dependent and subjective but I'm going to pause on buying Cossair 300Bs based on what you say--may not be worth it.  

Also, fyi, I run two subs with CW IVs. You are correct in that CWIVs are not bass monsters despite their size.  I love the sound of two subs tailored into the lower octave only.  

Finally, I heard back from China Hifi today.  They said that 120ma is the maximum you should bias the amp. They have no recommendations on what's ideal. They said that 100 ma (where mine maxes out with full bias) is fine and you can go lower.  

As such, 120 ma is the limit.  Your mileage may vary, but you may want to turn your bias down from 120 to (a) see how it sounds) and (b) avoid running the power tubes so hot to save life.  

My Carver Crimson has a recommended top end bias of about 100 ma, but Bob Carver says he likes the sound best at around 80ma.  Interesting. 

At any rate, the manual uses ambiguous language and I have now confirmed that 120ma is not the recommended bias setting but the maximum bias setting a user should use. 

@jbhiller  Yes, I think you are saving money not buying the Cossors. And the PSVane Acme really shine but they do cost a lot. Luckily we won a court case this year about a faulty installation. It dragged on for years but in the end the decision was in our favour and the other side paid in time. Otherwise I would´ve had to save much longer for these and the even more expensive 300Bs. My limited experience now is in line with what I read elsewhere: The expensive ones do stand out. So far I have not read about a cheaper secret contender. That´s different from the 6SN7 and 12AX7 positions, where even I could name some that can make you very happy for cheap compared to the expensive holy grails of (usually) NOS tubes.

Thank you for passing on the info on biasing. That´s really helpful and I will try it out as soon as possible. I never bothered to try other values since I thought that 120ma is the only one I should aim for. Improving tube life and (possibly) the sound at the same time – irresistable.

Chmaiwald,  I'm wondering if the stock 805s in the Willsenton R800i 805 are actually Linlai tubes. The reason I think that is some Linlai tubes, and their 805s, have a star shape at the top of the tube structure.  

Take a look at the photos here of Linlai 805 offerings and there's a star at the top: 

https://premiumvacuumtubes.com/product-category/shop_by_tube_model/805/

Do yours look this way? 

@jbhiller I´m not at home at the moment, so I can´t say with a 110% certainty, but I´m pretty sure they´re not Linlai. I haven´t noticed the star shaped thing at the top and as far as I remember the socket is golden – just like the PSVane Hifi.

I´d also be surprised if they put in a 450$ pair instead of a 140$ pair. Retail prices of course, but still. Maybe they couldn´t get hold of the PSVane and to fulfill the order took Linlai for yours? If so, congratulations!

FYI Chmaiwald, Linlai sells an intro 805 for $165 a matched pair (see that link above).