Upgrade capacitors in tube amplifier?

Yup I see 6 decouping caps also. They look like they are directional. But they look to be good caps.. IF there is NOT a problem, leave it alone. 
I don't think it's broke in yet, is it? 1000 hours or so...
Your one of those guys.. LOL Because it's there.....Right...

Is something missing, a valve roll won't cure? Why do you want to mess
with a new unit? Highs not high enough, lows not low enough...?
What do you want to change? Sound wise.

100.00 will buy some real nice sounding Green EH EL34 for under 100.00. Rubys, ReIssue, Mullard, 100.00 or so..

12ax7 or 12au7s, 100.00 no more.. don't get crazy.. Tellies, PVANE, GEs, Mullards, Volvo, Mazda, RCAs. BE CAREFUL with all the NOS stuff, a LOT of rip offs... I test EVERYTHING...MATCH the valves it will make or break the SQ, in both small and large valves..

Regards..

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