I have a pair of Mc275 MK V running in monoblock mode in my stereo system. I put all Russian Reissue Genelex Gold Lions in both amps in 2014. My assessment at the time was that the Gold Lions were much better than the McIntosh tubes they replaced. Lately, I was hearing some change in tone, so, I tested all the tubes last month. As you found, The small tubes were worn out, but, all the KT88s were in fantastic shape. I ended up changing out the small tubes - 12ax7 and 12at7. This time I went with vintage NOS tubes instead of the Reissue Gold Lions. I very much like the sound I achieved. So, based on this, as you already did, I would test your small tubes first and change those out before changing the KT88 power tubes. I cannot tell you about any sound difference between the Reissue Gold Lions and the Vintage Nos I replaced them with because the small tube Reissue Gold Lions were worn out. My impression is that you cannot go wrong with either Reissue Gold Lions or Vintage Nos tubes. When I need to change my KT88s, I will probably go with the Russian Reissue Gold Lions again. They lasted so long and my amps sounded so good for over a decade. I am not convinced I can improve on that. Note: My impression is that the small tubes have more of an impact on sound quality than the KT88 power tubes. Vintage NOS KT88 are cost prohibitive for me, so, I am inclined to select Reissue KT88 for their build quality and longevity. For me, Reissue Gold Lions have proved that to me so far.