I can give an example of what I have, as I didn't do a whole lot of research on other products.
My Pronto Remote operates over WiFi and has a base station that has 4 outputs for IR blasters. Each IR port has 2 basters which will operate 2 pieces of equipment. you paste the blasters (IR eyes in front of the receiving area of each piece of equipment)
If you are running 3 of the same Cable boxes, you would have to put them on different channels not the same channel. See
HERE
When you change inputs with the remote then all your doing is changing to one of the different audio signals, since the video is running full time.
So for example with the remote, you setup INPUT 1 to switch to Cable box 1 (audio) on the receiver, you control both cable box 1 channels, and volume on the receiver which is running on IR port 1.
If you switch to Input 2 on the reciever, you get Cable box 2 (audio) on the receiver and control the channels and the volume and that is setup on IR port 2.
Same thing for Input 3 and Cable box 3 on IR port 3.
With Pronto, you can globally tell the remote to use the volume for 1 receiver, and each input will have the ability to choose which IR port, and how you want to control that piece of equipment. They are complicated, but very flexible, once you figure it out, it comes easy. They set it up just like building your own webpage.