Sounds to me like you enjoy reading on the Kindle. We have a Kindle and a Kobo, my son uses the Kobo. There is not much difference in the reading experience between the 2 units, but the Kindle does have more features. I would suggest you get the new $114 Kindle that is ad supported and the buy a case. Cases range from $5 to 100 depending on what you want.
Etsy.com has some really nice hand made cases or you would have plenty left to get the official Kindle case with the light built in.
Amazon is working on something to make the Kindle work with the public library system so that may or may not be a problem down the road or as you have mentioned you already know how to convert books for the Kindle.