Just another thing to consider...the Opus21 is an excellent stand alone CD player, particularly with the GSNC reference mods. However, it may be that because of the high performance/value ratio, Jeff Kalt did not put alot of money or thought into the digital input? He may have just added a cheap off-the-shelf receiver for convenience.
A friend of mine, who owns a GNSC ref Opus 21, tried running my Wadia Ipod transport into the Opus and it sounded horrible...thin, brittle, just horrible. The same Ipod transport into my PS Audio DAC3 with Cullen mods was quite good, though just a bit shy of the Opus on its own. My Dell desktop with Lynx PCI card into the PS Audio was another matter, though. Into my Berkely Alpha DAC...pure heaven!! ;-) I am a computer convert now!
Good luck...it's worth the experimentation, but I wouldn't spend much money on cables or converters until you can test your current with a dedicated (even inexpensive) dac.
A friend of mine, who owns a GNSC ref Opus 21, tried running my Wadia Ipod transport into the Opus and it sounded horrible...thin, brittle, just horrible. The same Ipod transport into my PS Audio DAC3 with Cullen mods was quite good, though just a bit shy of the Opus on its own. My Dell desktop with Lynx PCI card into the PS Audio was another matter, though. Into my Berkely Alpha DAC...pure heaven!! ;-) I am a computer convert now!
Good luck...it's worth the experimentation, but I wouldn't spend much money on cables or converters until you can test your current with a dedicated (even inexpensive) dac.