Tubes

+ 1 tvad, better to be on the safe side, if you don't have a way to check the valves. Even if you do, have a way to check valves, one mans good on EBay is another mans junk.

Matched valves with ONLY 20% left in the tank are sold all the time as matched valves. They are matched for about a year if you're lucky..

Lets just call it worn evenly..  In some cases a small valve at 50% will last some people a lifetime, others maybe just a year or two..

Ask for quiet valves.. ASK, don't assume they will be.. Don't squeeze on the 6SN7 or the 12AU7. The 12AU7 is an easy one, Telefunken or Mullard Blackburn.

6SN7, is a different story, that valve is a Jekyll and Hyde history.. BE CAREFULL and choose a good pair.. 

PSVANE? How are you liking that valve OP? That's another Jekyll & Hyde manufacture, you just have to listen and adjust from their.. 
Telefunken and Mullard are going to be your friend with PVANE, I suspect. :-)

Regards

+1 @tvad 

Shout out to Jim McShane for tubes, too.

I have purchased the Melz 1578 from Svetlana_ua via ebay (100% positive feedback)(6 hole) several times out of the Ukraine. Zero Problems.
Have also purchased the cheaper Melz 1578 from markcohen-7 via ebay also from Ukraine with zero problems. Can still get "New" never used in the box NOS from these sellers and they ship immediately. Unfortunately they take a few weeks to arrive. Worth the wait. The Melz metal base are wonderful.

Ive bought a few items from Russia, solid transactions with reputable feedbacks. I haven't had the chance to test the PSVANE 845 yet. Will try tonight. 

I've never had the PS but read somewhere they take about 48 hours to open up. I like the paypal method of being able to protect your purchase also. Maybe it is my ears but the Melz sound better after a couple of days running. You probably know more about tube construction than I do.
Cheers.