I am using an AVA Insight DAC with a Marantz CD5001 as the CD transport. The DAC puts the music back in to the music. There is a lot more detail with the DAC. Without the DAC, the Marantz sounds veiled; a lot of the sounds just aren't there. The DAC is very musical, and the Marantz is very transistor. The AVA DAC has much better bass, too. Everything sounds better through the DAC. I haven't compared the AVA DAC to any other external DACs in my system. Regardless, unless a listener has a super standalone CDP, a decent DAC with a separate transport makes a good, flexible combination that would provide vastly superior sound compared to a standalone mid-fi CDP, like a Rotel, or a budget CDP, like the Marantz CD5001, IMO. There is an old thread on the AVA forum that compares an AVA DAC to a Cambridge 840C, a highly praised mid-fi CDP (approx. $1500.00).