"Someone comment on the SR Tranquility?  I'm not having much luck finding one to try out.  I like stability over tracking and speed."

never paddled one, though I ran into a guy along a portage trail (below the Piceral R dam) who had one - stopped to chat a minute and I asked him about his boat - it was a SR Tranquility (an older boat, maybe there have been changes, I don't know) - he hated it and was ending his trip early - it tracked too hard, i.e., was too hard to turn as far as he was concerned.  I've not seen any glowing reviews of the boat, more on the negative or ho-hum kind of comments, but I've never made a big effort to find review either.

you might look on Paddling.net or CCR.com to see if there are any reviews there.

I've never paddled a Prism either, but it has the reputation of being stable - it is a mainstay rental boat for BWCA outfitters - logically, they will choose a solo boat that is easiest to get used to for people who have never paddled a solo before - might be worth looking at for you

My first and only solo in a true solo was in a older model SRT that Quetico Dave had.
Like db mentioned, my pack set-up didn't really fit well in a narrow solo, but in the older SRT, it was particularly difficult, becasue the seat frame was a tubing affair that limited how I could place my packs.

I like my packs to be level or below the gunnel's for stability issues as well a less wind resistance. I ended up turning my packs on edge and that didn't help with over all handling one bit.

The seat was a little too high for my liking, so it's initial stably was very unsettling. Once in it and under way, it handled well in rough water. My first and only dumping in the Q was in this model was in this canoe, but that was as much my fault as its

The next trip I went to the SR 16 paddled with a double paddle and never went back. Suits my packs and my tripping style. Dave tried to get me to take the SRT again by lowering the seat a few inches which made a big difference in handling, but the pack issue was still there, so I passed.

I took a tour next year at the SR plan in Atikokan. I looked at the new model SRT and the issues I mentioned had been corrected. They now hang the seat from brackets of the gunnel's and the model I saw could be adjusted fore and aft, as well as the seat height with clips.
If would bring your packs/loaded and give it a try if you can. SR makes a tough canoe, if it handles to your liking then it might make a fine choice. Reviews are nice, but like buying any "vehicle", what counts the most is how it works for you