Hi all... Ive had my 730d for a while now...... One thing thats annoying is the sound system speakers and CD Changer.... In my old car i had a sub... which im not going to lie, i miss lol... First of all... can this system i have be upgraded of ease? Just abit more bass would be good? Also the CDC cd changer is not highlighted on the screen it ejects the holder and i can put back in.. but thats about it.. Any ideas? Thanks