Before you get lost down the tube rabbit hole, I'd encourage you to read up on 500c/800c restorations. Running your receiver on primo tubes won't do the receiver justice if the unit itself is sub par. Knock out the basics THEN run good tubes. You and the receiver will be happier for it.
To answer your question: I like sylvania 12ax7's (and they made a lot of military tubes.) Don't know why tho. I think it's because of the typical high gm so I don't mind chewin' them up. But unless you want to end up with a box of 20-30 various 12ax7 tubes, I'd zero in on a few mullards and teles for now if you got the scratch. If you want new, try the Gold Lions made in Russia, NOT the Chinese Gold Lions. Of course, a couple of LPS tubes unless you want to use the TADS in the phono stage. I've had JJ's die on me as well as Eh's. OK tubes but I avoid them for that reason.
Finally, I've learned that unless you listen to a receiver for a good while, you won't be able to discern any difference in rolling tubes. Bring it up to snuff, listen to what's in there now and roll a new pair in to see if there is a change. That test will really decide for you whether the cost of additional tubes is worth it.