Reddit mentions of Audio Adapter - 3.5mm Jack to 2x RCA Plugs (Discontinued by Manufacturer)

found it, http://www.amazon.com/Audio-Adapter-3-5mm-Jack-Plugs/dp/B000A3GPIS

edit: apparently you save $512, what a deal!

Here's what I would do to get a great sound system that will work for your ipod. This is much better than any ipod dock, but is not very portable.

1. power amplifier 50W/ch $103
   
   
2. bookshelf speakers $129
   
   
3. subwoofer $107
   
   
4. mini-jack to RCA converter to plug your ipod or any other device to the amp $3
   
   
5. speaker wire
   
   The total is over $300 but will be much better than the bose system. You could find cheaper bookshelf speakers that will work too.
   

First setup that comes to mind:

Plug Macbook/Turntable into the back using an adapter cable.

Plug PC into the back via SPDIF

Plug headphones in the front, speakers in the back, use the receiver to switch between sources.

This is the controller I use it’s $300 but it’s really good for the price https://www.amazon.com/dp/B01LXKL5IK/ref=cm_sw_r_cp_tai_kxYpzb680N51E
It doesn’t have aux imput, but what I did was buy this $3 adapter and it works really good with it https://www.amazon.com/dp/B000A3GPIS/ref=cm_sw_r_cp_tai_9yYpzbX6FY4ZZ
Hope this helps!