If an IR extender is in place, just use the native remotes. If only the extender wiring is in place, purchase an extender and use the native remotes.

Harmony is a DIY favorite and some models have RF capability. Note that you need a Harmony "box" to receive the RF and convert to IR. You may have a friend or child who could program the Harmony.

The MX-900 is intended for professional programming and there is a "box" (MRF-300) required for RF applications.

It's personal, but neither of these remotes is a favorite of mine because they have (in my opinion) a somewhat limited feature set, however, there are a LOT of these models in the field. If the previous owner took the equipment, but left the remotes, this is a statement about how fond he was of the remotes.

Not everyone needs a fancy remote and I often recommend using the native remotes, usually with an IR extender. Many of the latest TV's, ROKU, TIVO, and cable boxes use RF for their native remote. If you are lucky, the RF will reach to the equipment location (depends on distance, wall and floor density) When I do supply fancy remotes, they probably would be out of your price comfort zone, but I believe that you get what you pay for if the programmer is competent.