Dodgealum, I also have the P03 D03 G0s combo. Adding a G03x clock to the X03Se will make no audible difference that you will be able to hear. I have tried the G0s clock with the X01 limited player in a previous system of mine and in my dealers system as well - in both cases I could not hear a improvement. There is no doubt that moving to the P03 D03 will be a substantial improvement from your X03SE (with or without an external clock). I have not heard the P05/D05 combo so I cannot comment on that. If you do go the P03 D03 route, then at some point, adding a G0s or G0rb clock will make a nice audible improvement (not earth shattering, but a worthwhile improvement). The P03/D03 combo is a set it and forget it combo - the only real decision for you to make is whether you want redbook upsampled or not - and if so, to either 2x (88.2) 4x (176.4) or to DSD. Once you decide that by listening, you set it that way and it does the same thing everytime. Some people like upsampling others don't - its really your preference for your ears in your system.