Yes I know. It is a lot, especially when you’re first learning it. I can’t emphasize enough the importance of educating yourself on these topics, so that you can evaluate critically on your own, and not have to take someone else’s word for it. Taken in little bits at a time, you’ll eventually have it under your belt. Amir has tutorials, including some videos, that explain the speaker measurements, and lots of other useful things. You can use the search function at the upper right corner of the website. Put Amirm in the member box to get the postings that are specifically from him.
Since you like rock/metal, I expect you would appreciate a subwoofer very much. But, bass is one area where there is a lot of differences between individual preferences. Some like lots, others can’t stand it, and would rather not have subwoofers. I think lots of bass is really pleasureable, and I’m lucky that my wife likes lots too. It’s kind of a can of worms, in that you have to decide where to place the subwoofer, and where to do the crossover. These are topics of great ongoing discussion and debate. Many cross at 80Hz, or look on a FR graph to see where the output of their main speakers start to roll off, and cross there. It was suggested to me on this forum to try 100Hz, which is my current preference. When you start digging in to it, you’ll find most speakers have rising distortion below 125Hz or so, or even higher when the woofer is 5” or 6”, as is the case for many bookshelf size speakers. There are trade offs involved, so it depends mostly on what floats your boat.
What I look for when perusing “better speakers” is lower distortion, higher output (higher SPL), and better low frequency extension. You still want flat frequency response and smooth off axis behavior, of course. And then there is build quality, the look, the cabinet finish, and features. For example, powered monitors can have built in EQ, subwoofer might have built in crossover, whether the speaker accepts RCA or XLR or both, and so on.