I'm such a consumer whore. I said I was going to wait a while on a buttkicker, but here I am, having just ordered the parts to a kit. Soi-Fong asked me to let him know what buttkicker I eventually went with after doing some research, so I'll just post it for the entire thread instead.
Primer for those unfamiliar with buttkickers: a buttkicker is a brand of transducers built to strap to chairs. These are essentially the magnets from very powerful subwoofers. Instead of vibrating the air to make bass, these things, when strapped to your chair, rumbles your body. This does a couple of things - first, it gives the impression of enormous amounts of bass, one of these things is supposed to make it feel like you have an impressive sound system even if you're just wearing headphones (and side benefit: these things are silent outside of the chair, so others don't hear/feel the bass). Second, and more relevant to VR and games like Elite Dangerous - it'll essentially translate all the low frequency noises in the game (so, for example, stuff like the warp engines or the sound of your ship accelerating) into full body rumble within the chair you are sitting in. This is supposed to be amazing, especially in Elite Dangerous and Assetto Corsa.
So, after reading a bunch of reviews and opinions and articles, and shooting off some PMs to people, here's what I've found: Buttkicker Gamer2 appears to be sold out absolutely everywhere. These things are kind of like
the transducer to buy, but they've been hard to find for over a year now. Supposedly a new batch is coming at the end of august. These things apparently go for about $300 when actually sold according to some guys on reddit, although looking on google I found some stores that list them at about $150 (although they haven't had them in stock for over a year apparently).
Beyond that, buttkicker isn't the only option. A poster on
Reddit put together a list of parts for a kit he bought and assembled that apparently performs as well as these $300 buttkickers, only for less than $100. For those who can't be bothered to dig through the reddit thread, here's the parts list:
AuraSound AST-2B-4 Pro Bass Shaker Tactile Transducer by Aura Sound
Lepai LP-168HA 2.1 2 x 40-Watt Amplifier and 1x68W Sub Output by Lepai
12v 6a Adapter Power Supply for LCD Monitor with Power Cord by LCD AC Power Adapter
I saw some people vouching for this kit, and sent some PMs and got positive feedback, so I went ahead and ordered these parts. After shipping, the thing came out to less than $90. These parts should arrive on the 14th (!) so I'll post a quick guide on how I affix it to my chair and my impressions then.