I'm intrigued with the idea of sitting in my chair using my iPhone to control iTunes as it streams CDs I've ripped as AIFF files to a highly portable 1TB USB hard drive directly connected to an Airport Extreme Base Station that functions as an NAS. At the moment, I'm listening to Infinity Quantum 2s being driven by a '70s vintage Concept receiver. I have a MacBook Air connected to the receiver via the headphone jack to RCA aux inputs on the receiver. The MacBook is receiving its signal wirelessly from the Airport Extreme with attached HD (where the iTunes Library is physically located). It is very cool to see my iTunes library and control it via iPhone. Unfortunately, the sound quality is only OK for non-critical background listening in my opinion. Sound is rather thin compared to the original CDs. I'm assuming a DAC would help somewhat. I've also read about using the output from an Airport Express connected directly to the receiver's RCA inputs. Some say this would be an improvement. Alternatively, the Airport Express could connect to a DAC and then the receiver. Any thoughts, suggestions, actual experience with something like this setup? I know I can get a used Airport Express for under $50. Hard to know how much one needs to spend on a DAC.