If I understand it correctly, the only way to connect external speakers to the A850, without going through an amplifier, is through the Headphones jack.
Audio L/R outputs are Line-level (high impedance) and thus require another piece of electronics, if I am not mistaken.
As far as controlling the volume, the A850 manual says you adjust the TV and Headphones volumes separately. To me that means once you plug in the headphones, the internal speakers are muted, and Volume buttons will now control the headphones volume.
You can experiment with a pair of headphones to see if the remote in question does the trick. My guess is "yes," as long as it could control the volume to begin with.
If you don't have a pair handy, I can check later tonight and report my findings...
I am on day 5 of my new TV and just love the picture. However, the sound is fairly poor. I would like to purchase external speakers to use with this TV, any suggestions??? I am NOT looking for a full surround sound system. I would assume if I attached speakers I could just switch my settings to external speakers and they would work??? My last question is if I attach new speakers, would my samsung remote or SA8300 cable remote work to adjust the volume. I am trying to avoid using another remote control just to change the sound. Any help would be appreciated.