+++ ESL - Subwoofer combination +++

[scherffi]

Hello !
Looking for help complementing electrostatic loudspeaker
with subwoofer to get more natural bass/deep octaves
(but no BOOM-BASS !)

Currently I'm connecting a CD-Player's adjustable
earphone output to the input of a (small, 12Watts)
EL84-PP stereo power amp.
Now I would like to drive a subwoofer by taking the
CD-Player's same earphone output via an 'Y-Piece'
to a second EL84-PP amp I have and feed this signal into
a (small) subwoofer I still don't have.

Main Questions:
-Is it possible and wise to take the CD-Player's output to a very simple crossover (RC-combination-low pass for Subwoofer, second RC-combination-high pass for ESL)?
-How to dimension the RC's ? And how would the best crossover
frequency be determined?

Thank you in advance,
FrankieS