Silverarrows - I am on my 6th pair of Martin Logans and have always used an aftermarket AC cord. While I can't say it makes a huge, demonstrable difference, every little thing helps, especially with the high resolution that electrostats are capable of.
I have also read that Logans can benefit from using a power regenerator, such as a PS Audio PowerPlant, set at a different voltage (lower? higher?) setting, but i have yet to attempt this. You can probably find something on this by doing a search through the thread archives here @ the 'gon.