It kind of takes money to be in this hobby. If you want to try out subs, buy one and try it. Buy it used, so it's cost effective when you resell it. You can buy and sell, buy and sell, and keep repeating until you find something you can really settle on and be happy. It may take a while. Each sub sounds very different from another. I can't say I've used all that many subs, just 6-7 of them, and each one offered a very different presentation from the others as well as different capabilities and limitations. I've used a couple I've really liked. I've used a couple that I found very limiting or plain not that great.
Most products will operate fine over a narrow bandwidth, but not everything is capable for broad spectrum use. One thing I did was use the subs I had both in my Car and in my house. My house setup was a bit ghetto and paired the subs to a 1" + 4" satellite that required a sub to easily play up to about 150Hz at a shallow x-over slope. This pretty much required the sub to play to several hundred Hz cleanly in order to seamlessly integrate with the satellites. If the sub became sluggish, muddy, or simply introduced a lot of distortion or a messy frequency response, it showed problems. It was a good tool to measure the high frequency capability. There's also the matters of transparency, impact, speed, etc. that influence the end sound. A good sub in my eyes is one that can sort of do it all without any major flaws. The DIYMA is one of the best I've used in this regard. It's just absolutely transparent and doesn't faulter anywhere. You don't "see" it. The sound is just heard. Runner up is a sub no longer produced, my Sonicraft SC12NRT, basically developed for Madisound to be a poor man's Aura. It's a very fun sub as it offers a lot of impact and visceral sense, I think a lot to do with its mechanical efficiency excellent low end extension, as well as great transparency and usable frequency response range. RE Audio's SE12 is also a great, versatile sub with a very clean and controlled bottom end and natural sound. It isn't quite capable of a 150Hz x-over point running a shallow slope though and gets a little sluggish on the top end and sensitivity isn't great. These are the top three I've used personally.