Hi David,
While my parts have not arrived yet (it does take a long time from China... at least it is really cheap), I can send you a list of things that I have ordered or that I could recommend.
Starting off with the Microcontroller:
I am using an Arduino Uno Clone. You could go for the original Arduino Uno; however, that would cost you about 10x that much...
Here's a link to a generic arduino uno clone:
You can also make the project smaller by getting an arduino nano clone. For example this one:
To make everything look very clean, I have ordered the following aluminum knobs for the encoders:
http://bit.ly/2s9eYJYI am going to solder the pieces together using some kind of a wire... Some LEDs and Push Buttons would also be nice...
My plan is to put everything together into a box made of acrylic glass. I will make a separate post once the parts have arrived and I start with the project.
Using an app like "hairless-midiserial" it is possible to use the arduino clone as a midi device. Then it's just a matter of setting everything up and telling the arduino to send MIDI messages when the encoders are turned. You could even add buttons which would change the channel of the encoders. That way you could use 5 encoders to control 20 things for example...