Yes and it is not subtle. One cool thing, when you solder LED's they light up...
The difference in power is not something I've ever noticed, even with them side by side.
Anything from the PS900 should be interchangeable as they are pretty much the same device, albeit the 900 has a much nice chassis (die cast). The chisel tips are what I use most of the time though I have pretty much every one they make. SFV-CH25AR is what I've been using for the last few months....
Pretty much any film cap would work but it's that big as the cheapest caps are often 250V or so and also much more common. This was just lifted wholesale from the KGSSHV board.
No board run coming from us but any of you are free to organize one.
There would be a lot of wires running between the boards but yeah, it would be possible. Also, it isn't 100% clear from the pic but next to the heater connector there is a hole in the board to pass the wires through.
While the tubes will get hot it's above the caps so they won't see too much heat. Electrolytic caps are rated to 85-105°C but film caps can take way more than that.
Here is what I've been doing for the last day or so when time allowed...
This one has the tubes mounted on top of the board to make building and testing far easier. This version uses the old KGSSHV transistors and works with both the fancy teflon tube sockets and the standard ceramic/plastic stuff. This gives the added benefit of extra holes to cool the tubes. Boards are 4.7" x 4.7" and as soon as we are happy I'll order some prototypes.