Tube vintage: Amperex, Siemens, Phillips

I have tried a number of tubes in my DK-VS-1 Mk III and now I find myself gravitating to the following tubes: Siemens 7308, Amperex 6922 PQ and Phillips Miniwatt 188CC. Can anyone advise as to the best vintage for the above tube types or will any year sound the same. I have read that later model Siemen's are not as musical as earlier manufacture but have seen no documentation supporting this argument with the above Amperex and Phillips.

Thanks,

Anacrusis