DAC choice


I admit it, I am a bit lost on the topic of DACs. I have a Rotel RB-1590 amp and some B&W 804S speakers. I like my CD transport so far, although I doubt its DAC compares to a more dedicated one.  I do not think the amp or speakers are bottlenecks in sound quality, but am not sure I am getting the best out of my music, and I would like to get into more digital. I am trying to decide between getting the Rotel RC-1590 preamp with its DAC or a different DAC/preamp. I would welcome advice on preamp/DACs for $2,000 or less.
kumakahn
Optical toslink to the RME. From the RME you have a choice of RCA or Balanced connections to your Receiver. The RCA connections are small head connections will not take the larger head RCA's. 
I chose the NAD M51 over the Auralic Vega, PS Audio PerfectWave II and RME ADI-2, all of which I bought, tried and sold.  
More analog/natural sonic presentation (to my ears) than the others. Naturally, speaker pairing can influence one’s decision.  I have been using the Revel M106.