Balancing Resistor Values for Series Capacitors
As I understand it, you want to make a 1 kV polarized capacitor from two polarized 500 V capacitors:



The bleeder resistors are intended to keep the voltages on the capacitors roughly balanced.  OK so far, but this seems rather extreme.

The resistors will draw &frac12; A with 1 kV in!  That's 500 W of power, and  each resistor will dissipate 250 W.  This might work if you're trying to make a small toaster, but then you wouldn't need the capacitors at all.

Another way to look at this is to see when the result looks mostly capacitive and when mostly resistive.  The -3 dB point of 1 k&Omega; and 10 mF is 16 mHz.  If all your frequencies will be substantially above 16 mHz, then you're actually OK from that point of view.

I would look carefully at the worst case this circuit will be subjected to and see if the resistors can't be made much larger.

Dissipating 500 W just to avoid more expensive high voltage caps seems like a poor tradeoff.  Look at 1 kV caps, and also pop up a couple levels and re-examine why you think you need this in the first place.