I didn't have any "upgrades" done to my Cabernet but I did have a few mods. I have two balanced sets of outputs. The bigger one is that I can run either 6sn7 or 12sn7 in my amp. That cost me $500 but considering what the better 6sn7 tubes cost and how much less the identical 12sn7 I think I made the right decision.
Others have decided to use a pair of 6j5 per side instead of 6sn7. That would also be an effective way of getting great tubes at a much lower cost. I prefer getting the 6sn7 sockets though. I can use a 6sn7 to 2x6j5 adapter if I wanted to.