Adding a source to my Meridian system

My entire system is Meridian (G68 processor, G57 amplifier, G55 amplifier, and Meridian speakers) except for my source. Right now my source is an Apple Express with its optical output connected to the G68 optical input. This way I can stream music wirelessly and I can control my song selection with my iPhone. Pretty cool, convenient, and pretty (I hate clutter)!

But how about sound improvement? I think the source could be cleaner. I would be willing to sacrifice the convenience of being a couch potato and get up to change the CD if the sound were better. Of course, the obvious choice is adding a Meridian source. But would money be better spent for my system? Because the G68 has a digital coaxial input with low jitter and a good quality DAC, I would probably want to connect the coaxial digital output of a source to the G68 and bypass the internal DAC of the source. Does anyone disagree?

In that case, wouldn't my source need just a digital coaxial output with good signal integrity (low jitter)? I realize that a CD/DVD player may be able to decode some audio recording standards that the G68 cannot. But my music collection contains only CDs. So wouldn't I need just a transport rather than a CD/DVD player? After all, why pay for something that you don't use? What would be a good quality transport with a low jitter coaxial output that doesn't have so many features (like a DAC and other types of interfaces) that I would never use?