B_limo, thank you kindly. Regarding DACs, as you may have seen the OP doesn't have a separate DAC per se. He has the built-in DAC function of his CDP, and a DAC function that is provided in his vintage Sony preamp. I had suggested earlier in the thread that it might be worthwhile to compare sonics between the CDP's analog outputs and connection of the CDP's digital output to the Sony's digital input via a digital cable.
Regarding the purchase of a separate DAC component in the price range you mentioned, it's hard to say. A concern I would have, though, is that whatever benefit that DAC may potentially be able to provide might be limited by some combination of the jitter, electrical noise, and impedance inaccuracy of the CDP's digital output. A lot of people here and elsewhere have reported that digital transports often seem to make more of a difference than DACs.
Best regards,
-- Al