@curiousjim did you see the seller on the big e auction site selling the upgrade/restore kit for the ST 400? Has main caps too, two sets left and 9 sold.
I was wondering if you still listen to the amp at all any more or just storing it and thinning the collection?
Option-B: People do look for the amp and if you were using it once in a while, and lets say if you were still listening to it once in a while, you could buy the kit, keep it for a future buyer or find someone local to install it as another option. I liked my old Dynaco amps and when the right person comes along looking for one, decide then. Sometimes I'd like to have mine back to rotate in for fun once in a while. I liked the soft nature sound of that amp. Worked nicely with my electrostatics at the time, and I tried it with several different speakers, never a problem to drive many of them.