I have plans and buy a stereo encoder to my Max Pro 3.(Tired of mono sound now

Today, I have a cable between the studio and the transmitter, it's at about 90meter long with RCA plug in the end. I don't have much noise and any another interference, only a bad soundcard.
Will it work fine with a stereoencoder then? (it is boring and buy something that will not work so well)
Maybe it's hard to answer?
I have put a file with this post with a record from my station, so you can hear.
The file --> http://www.dump.no/files/6da61af97242/Untitled3.mp3
And another question:
Today my setup is like this:
Computer -> Mixer -> Limbo 1 -> Back to mixer (amplifies the sound) -> To transmitter
When I set the Limbo with the transmitter, the sound is wery low. Remains: The cable is about 90meters long.( I got to much loss) But when I do it like this: Computer -> Mixer -> Limbo 1 -> Back to mixer (amplifies the sound) -> To transmitter, it works good.
If I buy a stereoencoder, Do I have an extra amplifier? Or have the stereoencoder higher volume than the RCA plug on the transmitter?
https://www.pcs-electronics.com/product ... -encoders/
Long post

Hope someone can help
