EDM capacitors and voltage

Hi all,

I'm still working on the EDM project and have to make a decision on
which way to go.

From what I have read, the work performed is measure in joules. the
higher the joules, the faster the work.

If I go low voltage, I need a higher capacity cap(s) Using the
formula from the Build an EDM, it is
work(joules)=0.5 x capacitance X ((voltage)^2)

That said, a 700uF cap at 85 volts is roughly the same as a 100uF at
311 volts. (220 x 1.414 = 311)

Seems decent caps of high ratings are hard to find. a Motor run
capacitor is easy to find, are rated in high voltages, should work
but are limited to about 50uF in capacities.

If anyone knows of a good source for caps, please let me know.
McMaster Carr offers poly-metalized motor run caps for around $19.00
per 50uf@370V. stock #  7602K38 

Have I got this right ? am I on the right track ? does higher
voltage create any problems ? I'm hoping to avoid some shocking
discoveries.

I know all the good talk radio is AM thses days, but, I'll not mind
if I just create some static.

And in response to the recent request from our fearless leader, I'll
offer some thanks in advance to save the bandwidth later on.

Thanks in advance !

Dave