It could be that the Bluesound is generating a brighter sound with accentuated highs. The Audiolab and the Cambridge CXC could be producing a more neutral sound (yes, digital transports do not all sound the same). One additional reason could be due to the switching power supply on the Bluesound. Both the Audiolab and Cambridge appear to use fully linear power supplies.
Burning in the CXC should help, but I'm not sure if it will produce more high frequencies.
Burning in the CXC should help, but I'm not sure if it will produce more high frequencies.