Rotel RCD-1072 .... a DAC for improved sound ?

Please take a look at my system, and give me some ideas for an external DAC to improve the already terrific musical sound of my Rotel deck. I'm wondering if it's possible to significantly improve things, within the body of my very synergistic combination of components. ~$600 budget, including a decent "real world priced" digital cable. I have about a thousand CD's and 500 LP's (mostly 1950's and 1960's small ensemble jazz, female vocals, classic rock, and chamber music), and my listening time is divided fairly evenly between digital and vinyl. Also, if I buy a DAC, I'd probably like to be able to hook up a laptop for occasional internet muscic (Wolfgang's Vault, Pandora, internet radio.) Thanks a lot.