What amp/speakers? Do you have a preamp? Generally, some of these media players do have a volume control, but it’s considered a "digital volume". It adjusts the volume by modifying the digital stream. It’s said that you may lose some resolution on very quiet passages, but they usually extend the 24-bit word to 32-bit to do the volume calculations. In my opinion, having a true analog preamp with volume control would be better. But just having the network player straight into the amp will work too. I would probably lean towards the NA8005 for the discrete analog stages. I bet the Marantz would be great, but yeah, if you spend more (such as the Auralic), you could get better audio quality. I wouldn't necessarily argue for spending more - it depends on your threshold for budget as well as how far you want to go.
