Tubes on CJ MV60 and PV12

Hi there,
It is time now for me to change the tubes in my MV60SE and PV12A.
I had those now for about 3 years, they came with tubes not exactly new, actually one of the 12AU7 in PV12 already needs to be changed, sound became very distorted recently, swapping did prove that.
I know I can go with CJ for THE set of tubes that they carry for both devices, but I want to experiment a little. And hence my question for those folks how may be somewhat familiar with the subject.
If the statement that "not all tubes are equal" is not fully incorrect what are those that I should take more care about for better sound? I mean if tubes at the 'exit' make more difference etc...
The MV60SE has
12AX7 - 2
6SN7 - 2
6550 - 4 (can be EL34)
The PV12A has
12AX7 - 2
12AU7 - 3
5751 - 1.
And while we are still on it I have another question about tube tester, looking around I can see different ones anywhere between 20 and 300 range, pretty wide. If someone can give me a hint as to what I should be shooting for, want to have something around, mostly not because I envy giving 20 bucks to someone for doing testing for me, but mostly having to spend the time make me think I should be better off if I get myself one. Something that would tell me how close tubes will be matched, how much they have worked out etc...
Thank you,
For a special 12AU7 you want Amperex. There are lots of other really good ones out there though.