Over the last year or so, I've purchased and installed about 6 of these units in my home.
I built my house about 10 years ago and installed audio wiring and speakers throughout the entire house with the intent of installing a central audio system. Well, those audio systems were cost prohibitive and therefore a back-burner item. Also, over the last ten years audio system technology has evolved with advent of bluetooth and streaming services and everyone in my house has their own personal music tastes so the idea of a central system didn't make much sense for us. These little in-wall amps are the perfect thing to fit the bill. My speakers wire directly to the unit and all the sound control is done through our phones.
Regarding flexibility, there is a 1/8" stereo input jack that can be used to add signal from laptops, TV's or legacy sound devices like CD or tape decks. There is a 12 volt power jack on the front of the unit, so you can power it from a nearby 110v receptacle, but there are also rear connections on the unit for that input signal, and also for the power, so if you don't want to see cables running up the wall to the amp, there are provisions for that. Since my setup had wiring from all the rooms already going to one central location, I was able to use some of that wiring to run the 12 volt power to each of the units for a cleaner install.
Sure, if I had a wish list I would make some changes to these units. Mainly, I would like to see an on/off switch for the power. I have all mine in 2-gang boxes and use the other space for a wall switch to control the power, but that would be a nice feature for single gang installations.
I'd also love to see some infrared control of input select, power and volume so that I could control the unit with a universal remote without getting out of my chair. (I know, lazy, right?) But I wouldn't want these features if it meant sacrificing the quality of what's already there. These provide ample volume and sound nice on my Proficient in-wall speakers for which, I believe, is a reasonable price.
One of the units I received came with a part broken off of it, perhaps just due to shipping. The vendor promptly replaced the unit without any hassle. Kudos to them!
I still have a few rooms left that are wired for speakers, so I'll probably buy more of these in the future. By the time I'm done, I think I'll have spent about 1/6 the cost of purchasing a central system. Lastly, if I wanted all the units to get the same signal like on a central system, that could also be done utilizing the analog stereo input, but no, I'm good.