What's the reason for wanting to stream from a Time Capsule to your Macbook? If the Macbook is going to be co-located with your audio components, just attach a USB or Firewire hard drive to it and have that be the location of your iTunes music files.
The weak link in computer audio is the interface from computer to DAC. If you go Toslink, be sure to get a good glass fiber cable. If you want to go USB, either get a top-tier USB DAC (Ayre, Wavelength) or get a good USB to SPDIF converter, such as the HiFace, AR-T Legato, or Empirical Audio Offramp. That will open up your choices for DAC or Pre/DAC hugely. Be advised that most DACs that have USB inputs are doing a poor job of implementing and you will almost certainly be disappointed with the sound.
The weak link in computer audio is the interface from computer to DAC. If you go Toslink, be sure to get a good glass fiber cable. If you want to go USB, either get a top-tier USB DAC (Ayre, Wavelength) or get a good USB to SPDIF converter, such as the HiFace, AR-T Legato, or Empirical Audio Offramp. That will open up your choices for DAC or Pre/DAC hugely. Be advised that most DACs that have USB inputs are doing a poor job of implementing and you will almost certainly be disappointed with the sound.