IPhone 5S options for audio?

Have a look at Cypher Labs ALgoRHYTHM range or the upcoming iFi Audio iDSD.

The best thing is to find a digital docking station like the Pure i20 ($85 on Amazon) that has its own high-quality DAC or otherwise use your own DAC if you have one. The docking connector is the issue. Make sure its compatible.

Steve N.
Empirical Audio

You can now get digital out from an iphone5 using Apple's Lightning to USB adaptor under IOS7. The iphone will not power a USB-powered DAC. If you do get a USB powered DAC, you will need to put a powered USB hub between the iphone and the USB DAC. Check out threads on computeraudiophile.com. If you are looking for a portable product, there are more coming out every day (self powered is better, as the iphone will only provide a tiny bit of power). I have a JDS Labs C5D portable DAC/headphone amp. I think there are more portable options right now with the Galaxy phones, but there definitely are options for iphones and more coming.

Thanks all. Much appreciated..
Steve, how can an $85 docking station have a good dac? Isn't it just too cheap?