I have posted elsewhere about parafeed cap values. They depend on the plate choke value, with some adjustments for the specific situation. For the Paramours into a 4K load (which is the double transformer as I described it) and using the original 10 henry choke, 1.5uF is just about right.
The original Paramour used 3.3uF, which extended the deep bass for small signals but limited the power handling of the tube in the deep bass. I thought that was OK because the single transformer also had deep bass power limitations. With the double transformer (and assuming you have retained the stock 10 henry choke) the transformer can handle the power so I would use the smaller cap (1.5uF, more or less) so that the tube is able to deliver all the power the transformer can handle.
If you decide to replace the plate chokes with the 20H toroids, and replace the power supply resistor with the original 10H plate chokes, then the best capacitance would be twice as large, something nearer 3uF.
But in any case, it is always worth experimenting. Try the 1.5, try the 3.3 (original), try both in parallel. The quality of the cap will affect the midrange and treble; the capacitance will affect the bass (especially deep bass). When the deep bass sounds best, you can explore better caps in that value to optimize the mids and treble.
