My system

Technics SL MC7(110 disk changer) 10 year old and used as a transport.
B&K REF 30 preamp. Also used as DAC as my cd changer is connected thru optical cable.
B&K 7270 Multichannel AMP (200w X 7)
Paradigm S4 Signature fronts
Paradigm C3 Center channel.
REl Stata III sub

Are the DAC's of the preamps are of sub standard quality.

How much difference does the external DAC make compared to the one in a preamp.

Thanks
Pandu