Sony SCD-XA-5400 ES DAC Match

I have a Sony SCD-XA-5400 ES which I'm just crazy about. I've had it for three years and its my only source component. Is it possible to add a DAC to this unit and improve its sound. Someone at Audio-Advisor said I couldn't because its an SACD player(???)If yes, what would be some suggestions in the $1000 used range?

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