Hi and welcome.
I wrote a tutorial on how to get Audigy Rx working thanks to a nugget I found online. I copied its content and acknowledged the source. Sadly, many helpful reference sites have gone by the wayside hence my copycat approach at the start of the tutorial. I have my Audigy Rx connected to a Logitech surround sound system (Centre stereo, Front Left, Front Right, Back Left, Back Right, Bass). Be sure to read the entire thread. Crucial elements are to install all ALSA packages and emu-10k (Sound Blaster emulation package) using Synaptic Package Manager:
Also crucial to success is to install Audacious, covered in the same guide thread.