I've heard that G5s (especially dual-core/processor) really fly with 4 Gb RAM. Does anyone have one with this much RAM? If so, is it really worth the upgrade? I have dual-core G5 with 3.5 Gb RAM. It's great, but I do think it feels a bit choked at times. I would like to give it another Gig. What do you guys think? Worth it?