Personally, I would not attempt to control such a gaggle of devices with IR. I’d use IP control.

If you are price sensitive, a few bucks for a Raspberry PI (and a bunch of programming) will do the job. Depending on your programming skills and interests, a commercial control system may be a better choice. URC or RTI are probably your best choices because the others require large buy-ins and annual commitments.

The user interface is very important for a system of this scale.

Do you really need 24 separate DirecTV boxes? I don’t know your application. If you are serving a hotel or complex with TV’s in individual rooms, then you would need individual receivers for each room. In a bar, while there may be multiple screens, typically, multiple TV’s will be displaying the same channel. As mentioned, things have changed in the last 10 years. Now, there are switching solutions that can easily send each DirecTV box to any combination of screens over CAT-6. For example, in a situation bar where you might want to display three football games and a race, you’d only need four DirecTV boxes and each DirecTV box could be sent to any combination of screens. Depending on the switching system that you use, their software might be all that you need.