For digital playback I have a MacBook running as a dedicated music server. I use Play (free software, sounds better than iTunes, to me at least). Music is AIFF files on an external Firewire drive. Sound goes out via USB (making sure to use the USB bus that is not shared with other system devices like keyboard and camera). The USB DAC is a dB Audio Tranquility DAC. The computer sends all sound to the DAC at 16/44.1. I used to have a DAC that handled the higher resolution files, but high resolution seemed like a boondoggle to me. More than 95% of the music I own or would want to own is not high resolution, and a well-engineered DAC like the Tranquility makes those 16/44.1 sound like excellent vinyl (without the pops and clicks or other down sides). All of my high resolution files play fine and sound great as well.
I use the dB Audio Labs Essential USB cable. It makes a huge difference. I had the Alethias USB cable, and it was great. But the Essential USB, after about 150 hours break in, sounds much more open with better bass definition and impact. I'm very happy. I really don't need to hear anyone's opinion about how cables don't matter or how cables don't break in. I'm not into woo woo, homeopathy, astrology, ghost hunters, or psychic detectives, but physical differences in cable construction can make an audible difference.
Moving along, I am extremely happy with this system. It is better than anything I've had since I moved to CDs. It gets me back to the enjoyment of the music that I haven't really had since I started using CDs. Properly setup computer playback offers better sound for the price than any disc-based system in my experience. The detail, tonality, spaciousness, naturalness, and ease of listening are terrific.
I use Salk HT1-TL speakers, by the way, so I would say that I have a neutral/detailed system on the front end.