Tube info

There are more parts than tubes in an amp that affect sound. I have replaced noisy metal film resistors in $12,000 amps that had gone high resistance and very noisy.
Replaced them with wirewound resistors for better than original sound.
Of course coupling caps have been a target for replacement and should be explored. Power supply caps also has an effect.
The emission and gain characteristics from tubes is very voltage dependant. You could tweak the filament voltage a bit up or down, maybe 10 or 20% to see what effect it will have.

Jim McShane is my source .  He tests and tests and is very picky.  He will not sell you tubes without knowing what amp they are going into. 
@ Broussard that must be some private collection ! I consider mine large but don't have inventory like that. Well not as organized anyway.Yes Gl tubes can transform an amp I know, also the GL -KT-88s made a huge difference.  Good Luck 

@mechans, my personal collection could easily be called obsession or even addiction.  From 2008 to 2010, I acquired over 1,500 tubes.  

Fortunately, I regained control and am down to somewhere in the 275 range.  Still, entirely too many.

The adrenaline rush of buying or winning an auction is far out-weighed by the real work of prepping, testing, taking pictures, posting listings, answering silly questions, ignoring low-ballers, packing, and shipping involved in selling. 

Buying is fun; selling is work.

NOS RADIOTECHNIQUE 12AU7, very dynamic tube. 
I am liking what I am hearing with new production tubes at a fraction of the cost. 

@BBrousardI hate selling.  The perfectionist buyers who think they are buying from a store with unreasonable expectations .  I don't even want to think of the bath I'm going to take on some of my tubes.  I never really thought about selling, and therefore keeping track of what I spent. I would leave it to my heirs but they will probably end up giving them away.I like my tubes and really don't want to sell.  If I did I would buy more to replace them.  What I am going to do with all my 6SN7s I'm not sure, I have a couple of dozen of Ws alone.  Some great some not so great.  I am too honest to be a good salesman .  Telling people AS IS, AS Found, ETC. when I know better.