I got a backpack style subpac for vr games. I was putting it on in the chair but it was a bit uncomfortable so I decided to get a AuraSound AST-2B-4 Pro Bass Shaker and Dayton SA70 amp from parts express to power it. I filed and drilled out some spots on a thin square piece of wood so I could put it flush against the bottom of the metal part of my chair and epoxied it there, then I mounted the aurasound to that so that way it has a solid fit to the chair and I can always take it off fairly easily when the chair wears out). It provides plenty of shake although the amp sucks balls, the cutoff does almost nothing and some treble sounds come through (luckily I mostly play with headphones or up so loud I don't notice it).
If I had to do it again I would have not bought the subpac... I would have bought a different amp that could power two of them (probably not a dayton given my experience with that one), I would have still bought the aurasound shaker it's a cheap diy sort of kicker but it's definitely plenty good for gaming, but I would have bought two and I would have put one on the bottom of the chair and one in the mid back.
Anyway in terms of what they add... they are really cool. They aren't the end all of gaming but they do make the sound seem a lot more cool. You wouldn't believe the sensation of bass they give, then you stand up and just hear a mild vibration, you sit down and it's like there's a sub in the room. I will admit the aurasounds dont simulate the full range of bass like the subpac I have does...that thing is practically musical, but all I care about in game is the womp of the FSD and cannons and things like that. Basically if you have a little extra money and time they are a fun project and very enjoyable. I wouldn't put them up there with getting a hotas/thruster or a solid computer rig with a really good monitor though.
In addition to what I described, I also bought a few banana plugs (male and female), speaker wire, and connectors I needed from monoprice. The reason I got the banana plugs is because I glued the females to the bottom of my chair so that I can just plug and unplug the speaker wire when I want to move my chair away. I have VR and cats so I don't necessarily want to just leave my chair in the way with wires hangin' off it all the time, and the bass shaker has those standard sort of speaker clamp things so they weren't as convenient to plug in as banana plugs are.
I have a pro audio soundcard so it was not hard for me to use extra outputs on my soundcard for the amp going to the shaker, however there are ways of rigging output if you have onboard sound card... like apps that let you use the surround outputs on your motherboard sound and stuff or using an extra cheap usb soundcard and a program that lets you mirror audio over two outputs.. I don't really know the particulars since I didn't have to mess with any of that but I'm sure you can figure out how people without pro audio cards are sending audio to their speakers/headphones and the amp that goes to the shaker without too much effort.... but that's something to consider and figure out before you dive in so throwing that out there as well.
The subpac I have does wireless but it seems really delayed so it was kind of useless. It also has an amp built in. They also make a chairback model which is probably a lot better than the backpack one I have for sitting in a chair. Also they are like 5x the cost of getting the aurasounds i mentioned above so not really worth it IMO... They are a real good product, but I feel not worth it. Perhaps if you are an electronic musician who lives in a small apartment or somewhere where you can't have a subwoofer, the subpac would be a pretty good compromise for that situation I think.
Anyway that was a bit of a ramble but figuring out all that was a process for me so I wanted to kind of relay it so you could maybe consider some other options without spending years on the internet googling and forum crawling