Do 5.1, unless you have a need for an extra channel, which you probably don’t.
With the video source that I got, Final Cut Pro didn’t give me the option to put it into surround 😕 Some clips were in dual mono, so I got that fixed, though. I have a new version of the opening ready to upload to Vimeo, but the wifi currently isn’t working on that computer
You could rip your dvd or blu-ray and mux the stereo audio to your video source
Also, I’m looking forward to your new intro!