USB-to-S/PDIF converters:
Bel Canto USB Link 24/96 USB-S/PDIF converter. Here's Stereophile review: http://www.stereophile.com/budgetcomponents/bel_canto_usb_link_2496_usb-spdif_converter/index.html (now $249 instead of original pricing of $495)
M2Tech Hiface (supports 24/192 files). Here's 6Moons review: http://www.6moons.com/audioreviews/m2tech/hiface.html
This one received 6Moons' Blue Moon award. This would be my choice at $150-$180 and supports full hi-rez files.
USB DACs:
Too many to mention. What is your budget? You can do HRT Music Streamer II ($150) and II+ ($350) all the way up to Ayre's QB9 ($2500) and more expensive offerings from Wavelength. There are many other DACs that have USB ports but the ones mentioned above are optimized for USB and use one form or another of asynchronous transfer mode, where the DAC slaves the PC to the DAC's clock, reducing jitter and to my mind is the superior DAC technology via USB port.
You should check out Computer Audiophile (http://www.computeraudiophile.com/). Many good resources and reviews there for everything related to computer-based audio.
Hope this helps.
Bel Canto USB Link 24/96 USB-S/PDIF converter. Here's Stereophile review: http://www.stereophile.com/budgetcomponents/bel_canto_usb_link_2496_usb-spdif_converter/index.html (now $249 instead of original pricing of $495)
M2Tech Hiface (supports 24/192 files). Here's 6Moons review: http://www.6moons.com/audioreviews/m2tech/hiface.html
This one received 6Moons' Blue Moon award. This would be my choice at $150-$180 and supports full hi-rez files.
USB DACs:
Too many to mention. What is your budget? You can do HRT Music Streamer II ($150) and II+ ($350) all the way up to Ayre's QB9 ($2500) and more expensive offerings from Wavelength. There are many other DACs that have USB ports but the ones mentioned above are optimized for USB and use one form or another of asynchronous transfer mode, where the DAC slaves the PC to the DAC's clock, reducing jitter and to my mind is the superior DAC technology via USB port.
You should check out Computer Audiophile (http://www.computeraudiophile.com/). Many good resources and reviews there for everything related to computer-based audio.
Hope this helps.