Upgrade capacitors in tube amplifier?

In a tube circuit the higher the voltage the better 600v is optimum 
the vh Odam is a excellent cap ,the VH Cu Teflon caps even better 
if it will fit and can afford.

I know this not a tube rolling thread, but I would suggest swapping the 12ax7 and 12au7 tubes first. I recommend trying some 1950's vintage Raytheon black plates. Try to stay around $70 for each tube. For the power tubes you could get some 807 tubes with an adapter.

My advice is, if you’re going to change coupling caps, stick with the various film and foil types, rather than a metallized film. They’re generally more expensive (but not always, depending on mfgs), but are of better construction, especially in regards to lead attachment. In a film & foil cap, the foil protrudes at each end of the rolled cap, and the lead is soldered or welded directly to the foil . Metallized caps have the dielectric protruding at each end, so a conductive paste is applied, which makes contact with the plate. The lead is then attached to this paste (a less reliable form of construction).

 Be aware that, for equivalent voltage ratings, film & foil types are generally larger in overall size.

Another vote for tube rolling first and caps maybe after 750-1000 hours of listening.

All the best.

JD

By the time you install Nichicon caps, V-Caps and some Audio Note resistors you will probably spend half of what the amp costs new.  IMO the Chinese amps are below average in sound and if it were me, I would buy something else - I know that you don't want to hear that sorry. The caps and resistors will open up the sound and probably proved improved bass and dynamics if you want to travel down that path.

Happy Listening.