Looking for docking station with hi-rez digital output.

Hi folks, I found that i have older iPhone leftovers and wonder if i can still use them as dedicated WiFi streamers (such as youtube) and players with few hi-rez albums in limited 16 or 32g space on them. I plan to use several of my 4s and 5s with different albums saved and keep them as storage as well. I'm looking for descent performer that can accommodate both multi-pin and lightning ends with perhaps multiple docks. Professional (pro-audio) options are also welcomed. I also wonder if I can just plug in my iPhones directly to DAC. Is there any specific app to use to make it happen? What will be the advantage or disadvantage over the docking station digital output?

My beloved family upgraded their phones shortly after me g5 to g7. After this rapid upgrade of nearly 6 phones, Not only I realized that they worth fnothing, but remaining ones to pay-off dropped their used price also to a substantially lower than I owe for all of them. This situation indeed made me bitsy fangry. 
I used my ipod Touch as a streamer with Luxman ipod dock...sounded quite good. D100-r, and used Apple adapter for lightning for newer Touch

The Nuforce Icon iDo will extract a bit-perfect digital output from an iPhone via either 30 pin cable or Lightning cable. It has a built-in DAC and headphone amp. It outputs either analog via RCA connectors or digital via toslink or coax.

I use one with both older 30 Pin iPods and newer Lightning iPods. Also when friends visit, they connect the cable to their iPhones to play from their playlists.

The Nuforce Icon iDo is long out of production, but usually sell for $49-$99 on eBay.
Hi.I have 2 of the Pure i-20 Docking Stand/DACs for iPhone mint condition and complete in the boxes...I have no way to check them out but if your interested let me know and we'll work out a deal...