As you noted, the K4 Touch will be released shortly. The SO K4 Touch will cost $99. It will have the touch screen that you like and will be very similar to the Nook.
If you are comfortable stripping DRM then you can shop at Amazon and read on your Nook. If you want to move to Amazon for any reason, you can strip the DRM off of your BN books and convert them to put on your new Kindle.
I would get the device you are most comfortable with. The features are pretty similar and the book stores are pretty close in terms of popular, main stream reading material. If you have been able to find books on Amazon and not on BN, then wait for the K4 Touch and make the move. If you are not having trouble finding the books that you want and you don't want to strip DRM and convert, get the refurbed Nook.
I think you will be happy either way.