I'm buying an iMac G5 in a week or so (20" 2Ghz!) and I'm curious as to what speakers to buy to take advantage of the optical audio out. I haven't owned or heard a 5.1 system before, would they be worth it? Would an optical-based 2.1 system sound better than an analog-based 2.1? Also, if I bought a 5.1 system, would my stereo music play through all of the speakers? Thanks!