It seems "positive experience" is hard wired in to every single living thing on earth. For trees, the sunlight is positive experience because it provides energy. Sounds ridiculous doesn't it? But you are the one talking about inert matter needing to have "positive inner experiences".
Why would pansychism derive egoist organisms? It would be more intuitive to think the opposite, that all organisms are one and therefor have no need to serve a segregated and individualized egoist motive.