I wouldn't be afraid of crossing over the PS210s at 50 Hz if the electrostats can actually deliver down to 48 Hz +/- 3 dB as I believe they have a rated frequency response of 48 Hz to 26 kHz +/- 3 dB. Try several different crossover points, you may find 50 Hz sounds best. The PS210s have a steep 24dB/Octave crossover slope and the two (ESLs and subs) might perform better overall crossed close to the effective low end range of the electrostats.
I also wouldn't be afraid to move the panels out into the room a bit, even perhaps following the Cardas Golden Angle theory:
http://www.cardas.com/pdf/roomsetup.pdf Those electrostats radiate from the back as well and you may find more depth in the soundstage with them out from the wall a bit.