Steve, 
You don't need to keep adding more resistors
and caps. 
Just change the resistors and leave what caps
you have in the circuit. 
Basic Ohm's law stuff here. 
If you need to drop the previous stage's
voltage an additional 100 v to get your new
final B+ down to 285v (and you are only
drawing about 3ma), then you divide that
100v drop by the 3ma. 
100/.003a= 33K-34K, 
This works fine on the last resistance in the
string. 
And if you know what the total current draw
is through the resistor ahead of the last one
you can go back to Ohm's law again to figure
a new voltage drop but now it will effect the
overall drop to the very last stage to because
there was less to work with anyhow. 
In other words: 
If the last stage in the B+ rail is feeding one
12AX7 and the current draw is 3ma then...
see up above. 
And if the last stage is feeding two 12AX7s
then you have to double the current and
divide the voltage drop by the new expected
current draw of about 6ma....
100v/.006a=16K-17K. 
But, if you were working to drop the B+ in
the stage ahead of the last one, then you have
to allow for the current draw from the very
last stage and the stage you are working on. 
All the current drawn from the supply strings
have to go through the stages that proceed it! 
This applies all the way back to the very
begining B+ from the rectifier. 
So dropping the value of the first section is a
good first step, then work your way to the
end. 
Every drop you make in the begining will
give you less B+ to work with as you come to
the last resistor in the supply line. 

If that didn't confuse you ...you're hired! 

Lower voltages seem to warm the stage up a
wee bit, go into distortion a bit sooner, and
lessen the overhead too. 
On the driver PI, I like to see the plate load
resistors being fed with about 300V to 350V
and the first preamp section, 250V to 300V to
the plate load resistors. 
This can get to be a personal taste thing so
don't knock yourself out. 

Bruce