Upgrade capacitors in tube amplifier?

@chinook9

" 1extreme, I realize the circuitry is very different. Generally, do you think there is less potential for a coupling cap upgrade to be as effective as a crossover cap upgrade?"

The answer to that really depends on the other components in your tube amp and the other audio components in your end-to-end audio chain. Do you believe those two coupling caps are really the weakest link in your end-to-end chain? If not then it is unlikely that any improvement would be "revealed" by your system. BUT....this is also about having fun so if getting in there with your soldering iron and swapping components and trying to hear the difference will bring you fun then go for it. Been there and done that, so I’m the last one to poop a fellow audiophiles party.

There are three coupling caps. The first is at the top of the photo, one in each channel. To the far left and right beside the power tubes is a small circuit board; the coupling caps for the output tubes are mounted on that circuit board; they should be matched for best results.

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.