As Tony said, I used the docking cage connectors, which are also female (hence the need for the male-male connector). These are supposed to be 4v. I used the front pair (no rear speakers in the Boxster by default). Hence no need to do anything special to remove or replace.

Volume is set permanently at 0db, I use the Becker volume control [hence- would be great to use the empeg rotary control for something else than volume without needing to press it]. Sounds fine, not too loud or distorted (though going over 0db into overdrive definitely does sound distorted). Sounds same volume as the radio or CD when switching to that, maybe the Becker compensates somehow?

Anyhow, sounds great to me :-)