You did not mention how your BD player is connected to your amp (I assume HDMI) because that determines where the D/A conversion is done. Also what speakers do you use?
If your amp also has an Coaxial spdif input, look at the Hifiberry digi+ (pro if you want to go the extra mile) or the upcoming Digiless from Allo. This way you feed the amp a digital signal (as you do with the HDMI) and again do the D/A conversion in the amp.