Third option: If your iPhone is pre-Lightning. Get a dock to RCA cable. Analogue to your system but bypassing the internal headphone amp. RAM Electronics have decent cables for $30.
I love the HRT iStreamer DAC for this. Everything you need for $200 except the RCA cable from the DAC to your preamp/integrated. I like four things about it:
1) It bypasses the internal DAC. Sounds pretty damn good for $200. This works not only for your iTunes music and ripped files, but also for anything streaming to the device, such as Pandora, internet radio, YouTube videos or movies.
2) Very portable. I can leave an RCA cable attached to multiple preamps/integrateds around the house and just bring the iStreamer to another room if I wish. It can also be powered from a cigarette lighter adapter and used in the car if your stereo has RCA inputs for an aux source.
3) It charges the iPhone while you are using it.
4) I use a longer RCA cable from the DAC to the preamp so I can keep the iPhone/iPod/iPad next to me. It's nice when I want to hop around from internet station to internet station.