Well, for me, I wanted at least 200 watts RMS and perhaps 300. RMS it the important spec here, not peak. RMS is what our ears hear. I don't need a thousand watts RMS but your mileage may vary. So I needed to purchase a sub capable of that power and an amp capable of producing that power without straining. I wanted a sub that would fit under the rear seat, which means the box I chose had to fit under the seat and the sub had to fit in the box. It's also important that the sub you choose performs well in the space the box provides. This is called volume (which is physical volume, not audio volume). If the box is too small, the sub can't perform at its best. Ditto if the box is too large, although this is rarely a problem in vehicles. You will find this spec stated for the subs you may be looking at, as well as the box. By the way, I don't think any of the subs in the article in your link will fit under the rear seat of the 5th generation RAMs. We need so-called shallow subs to fit under our rear seats. Fortunately, manufacturers have come a long way in recent years with these shallow subs. Their performance is actually surprisingly good. I also needed an amp whose impedance would match the sub set up, which in my case, is dual subs. My subs are 4 ohms each wired in parallel, which presents a load of 2 ohms to the amp. So I needed an amp that was capable of a 2 ohm load. Most amps for subs these days have two types of inputs, low level and high level. But not all. This is important because if you are tapping into an existing speaker line to feed your sub amp, you need a high level input on the amp. If instead, you are running the amp input to an output on your stereo unit, you will typically need a low level input on the amp. Another couple of things to look for on the sub amp are a cross-over frequency adjustment (typically recommended to be set at 80 Hz but some may prefer a slightly different frequency--flexibility is good!) and an input level adjustment. If you overdrive your amp, you will get distortion and be very unhappy. And one more thing, most of us like to have a remote adjustment for the amp. That is, a control that will be mounted on or near the dash and wired back to the amp so that you can turn up or down the amount of bass that the sub is producing. I can turn mine up so high that it rattles my windows and vibrates the rear seat so much that no one will enjoy sitting back there, but most of the time, I have it turned down to a more reasonable level where I am enjoying hearing and feeling the bass but it's not causing everything to rattle.
I've stated a lot of information here. The thing I did was read a lot of professional reviews as well as those you find on Amazon. I was able to glean a lot from those. I did the same for sub amps. I didn't budget an unlimited amount for this upgrade so I needed to match my desires with my budget.
Ideally, I would have found a sub box with built in sub and amp, like the MTX Thunderform that I had in my F150. Loved that thing. And there are others out there. Unfortunately, I could not find one for my new 2019 RAM in early 2019, so I wound up piecing together my own system. At some point, MTX and others will come out with "plug and play" sub/box/amp setups for us. There might even be one out there now...not sure.
