Bwoca,
So, your xover works with +/- 16V. I think you have a couple of possibilities here too:
- the virtual earth proposed in ESP demmands modifications in your xover and has little output current capacity. I think it would be a little hard to implement in your case, but, if you decide to go on this way, I can say usually +/- 16V circuits will work fine with +/- 12V;
- I´ve built, many times, a simple self oscillanting circuit to feed this kind of gear. It works on 30 or 40 KHz and you can use 3 terminal regulators at the output to regulate it. It´s easy to mount and you can find the components in any surplus store. If you were interested, let me know and tell me an e-mail address when I can put the schematics and other instructions. Of course, it demmands some electronic skills, but you can mount it without mess your xover and learn enough until felling yourself confident to connect it to the xover.
Regards