LOL! 
No shortage of opinions here 
I assume you like your pre, and it looks fairly will built. The pot could be better, but you are correct that the caps are the bottleneck. The "douch" caps are probable just one of a dozen rebadged metalized SCRs. They appear to be in the power supply, and less important locations. They are probably OK there. The tin foil Solens are not bad on the cheap, but there is a whole lot more to be had. The tin foil cap is a larger cap, so it is possible that a reasonable value will fit in the output location. The interstage is more of a fixed value, but they appear to be small values. We are only talking about changing two pair here. The Jupiters are likely the way to go, but I would like to hear your desired results, and see a schematic. If a schematic is not possible, you are welcome to send it to us for a free evaluation. You will only be obligated to return shipping. We will tell you everything there is to know about it, and if the Jupiter or brand X will fit.
No disagreement here. Although depending on who you talk to which one of these upgrades (cap versus pot) would be the 1st? Difficult to say without seeing a schematic to be honest. And if it were me, everything would be reanalyzed including bias points, output transformers, etc....then suddenly you have a different amplifier! For me, proper circuit design is paramount, along with measurements...then and only then do you populate it with 'fancy' parts if needed. There are a lot of average performing circuits out there, caveat emptor.
I'm not much of a modder sadly, I have completely drifted into the 'build it right the 1st time' camp. But that takes a discretionary income that many do not have.
Thanks for your experience & patience Jeff

, I actually have an
AMP CAMP F4 order coming your way...I'm curious about how that circuit performs...but with some of my own twists thrown in

Best,
Anand.