I have a 2009 Highlander Limited and am planning to install an aftermarket audio system with an XM radio receiver. Does anyone know if the "prewired" XM antenna connector in the 09 Highlander is compatible with aftermarket XM receivers, or does it have some kind of proprietary connector that will only plug into the Toyota XM module? From other postings, I understand that this connector is in the dash near where the audio unit installs - correct?