Computer, Airport Express, DAC - Best Sound?

I have a G4 computer with itunes. Music is on HD using Apple Lossless. I have an Airport Express and a Birdland DAC connected to my stereo system. My current connection is mini-toslink to toslink on the DAC using the Airport Express (Monster) optical cable.

What's the best way to optimize this system for the best sound? Should I get rid of the Airport Express and use a Waveterminal and coaxial cable?
The sound is nice and clean. However, I'm always looking for improvements. Would a glass toslink improve the sound over the Apple Monster toslink? My concern is that even with a glass toslink, I would need a mini-toslink adapter. Would this adapter defeat the advantages of the glass toslink?