You mentioned going an octave lower... I am on a quest to get a baritone uke tuned to gcea, a full octave lower than the standard GCEA tuning. To that end, I have ordered a Kanile'a baritone through the uke store U-Space in Little Tokyo, Los Angeles. The guy who runs the place, Jason Arimoto, says that he will play around with different strings to get the right sound, but that it is doable. Since he is a MUCH better musician than I am (or will even be), I asked him to record a YouTube video or two showing off the tuning before he hands it over to me, so other people can hear what it sounds like. I was only able to find one video, and the guy didn't really go into much detail on what he did. But it sounded great!
Sorry I can't advise you on what it sounds like right now, but give me a couple of months, and I can.