Need tube help!

As @oddiofyl mentioned - NOS are $$$. But once you experience them, it is painful to imagine life without them. And this is coming from a person who resisted tubes for couple of decades.

You can try the Gold Lions or Psvanes. In the "current production" lines, the Psvanes are couple of steps above the Gold Lions or anything else. I speak only for 12AU7s since I do not have experience with KT88 or 12AX7.

Lots of folks like the Gold Lion KT88. I don't see how you could go wrong, but I've never listened to them. If they are available they do cost about $100 apiece. I've used and still do Tung sol 6550 in my Dialogue 2. I suspect from what I've heard folks say about the Gold Lions is that the Tung sols might be a bit darker in tone. They are selling for about $85 apiece now. Any darkness can be compensated for by selection of the 12ax7. I'm presently using EL 12ax7's and 12au7's with them but they are hard to find if you even can and somewhat expensive if you do. I've used Mullards and JJ's 12AX7. The former is on the bright side but does open up the Tung-sol's, the JJ's are an underrated tube I think, but they are mid-range centric and will tame a bright power tube (or system) some.

If your unit will accept smaller power tubes you should consider the 6L6GC. It is a very neutral tube (in general) and tonally is similar to a good 6550 or KT88. Linear, clear, and not thin or bright. Just less power. I've used SED 6l6gc's in my Dialogue One and just loved the clarity. But as with many of my tube stash they are no longer in production, ergo hard to find and costly if you do. 

I tried the Mullard KT88's - they didn't appeal to my ear much. Bass was fulsome - I like tighter bass (on my system).   

Presently new production tubes are hard to find and prices certainly have gone up!

BTW, FWIW, if you feel desperate to experiment, and are willing to give up a bit of bass power, you can play with a set of JJ E34Ls and some of their small tubes. The power tubes cost a bit over $25 each and believe it or not their small tubes cost as much or more. The power tubes can light up a dull system with out being aggressive. :-) 

BTW, personally speaking, I would not invest my money or yours  on "NOS" tubes for our Primaluna integrateds. 

As this might really apply to you with your stuff it really is not much more than a WAG! :-)

I would definitely listen for a long time to the tubes that came with it. You want to know your system… this is your reference. Then think about changing things, 

Study the PL website resources. Acclimate your ears to "the sound"

Otherwise, you're just going to waste money, not knowing why you're changing tubes. The stock tube set will sound good if the rest of your setup is solid.

Maybe three months ago, I phoned Upscale Audio and asked for some fresh power tubes for my several year old Primaluna Prologue Integrated. The guy at the other end of the phone grunted and asked me what kind of music I like. I said classical and he recommended 6550's. I've probably had my Prologue for better than half a decade. I like the guys at Upscale and just said yes. The 6550's showed up surprisingly quickly. I plugged them in. After a couple days or so of break-in, they're now making me very happy, indeed.