Clocker value on a network player?

With the exception of USB and Ethernet, all other commonly used digital audio interfaces (spdif, toslink, AES3, i2s) are synchronous. This means that the source (the network player in your case) controls the clock.  

Some DACs will buffer and reclock even these synchronous interfaces, but it's still important to have an accurate and clean source clock to reduce buffer under/overflows and noise. 

Many DACs sound better using one of these synchronous interfaces. For example, my Denafrips Terminator Plus sounds noticably better using i2s than any of the other inputs I've tried including USB. 

Synchronous simply means that the audio data is sent to the DAC at the same rate that it is played (e.g. at 44,100 samples per second in the case of standard Redbook CDs). The DAC has no control over the rate at which the data is sent. 

Asynchronous means that the DAC periodically requests a bunch of audio samples as they are needed and the DAC controls when to do these requests. 

Theoretically, an asynchronous USB connection should eliminate any sonic effects from the upstream components because you are just sending digital data and the DAC is in complete control. 

In reality, it usually doesn't work out this way. It appears to be fairly hard to isolate the noise created by the USB interface itself from interfering with the sound quality. Moving the conversion from asynchronous to synchronous outside the DAC often (but not always) results in better sound quality. 

Even DACs with exceptionally good USB circuitry and noise isolation benefit from a cleaner USB signal, although how much depends on the DAC. 

There are no easy answers here (and a lot of differing opinions).