I posted here a couple of years ago that I had bought a ButtKicker. I was mocked at first, until Bermuda chimed in. I think that their usefulness is often misunderstood.
After Bermuda described his rig and that he was using two of them mounted to his throne, I ended up buying one more unit. The reason being that they can be switchable in case they shutdown from over heating when they are driven really hard.
The first unit I bought I mounted to my Roc n Soc with the BK bracket. Once again at Bermuda's suggestion, when I got my second unit, I skipped using the mounting bracket and now they are screwed in directly to the bottom of the throne. I can feel it much better.
I am using a Crown XLS1000 and it works well. I don't think I need any more power but I think Bermuda uses a little more powerful amp for his.
One thing that I do that is a little different is that I am not running the kick drum mic back to the unit. I bought a Simmons accessory pack on sale at GC for $200 and it has two pads, two triggers and most importantly an inexpensive e-drum module. I'm triggering the kick and the module sends the signal to the BK. It makes it very simple for me to get good monitoring without fussing with my kick sound.
With all that said, the truth is that I have not had the opportunity to use it in a concert setting. I just don't have those gigs. I bought it mostly because I liked the idea and I had a little money to spend. I leave it set up on my rehearsal kit. I've only taken it out once and it was a total PITA. For me it's a luxury item but it is truly a wonderful way to monitor your bass drum and the tactile monitoring honestly does make you "one" with your bass. I immediately felt that I could be more precise and or "tighter" so to speak than before.
I could absolutely do without it, but I think once you try one or moreso, once you play with one for a little while, you will want one. I was first exposed to this when a friend bought a gaming chair for his video game gear. I'm a 100% positive that if you are in a louder music scenario and you have problems hearing your kick drum that a BK will change your mind forever.
The Porter & Davies set up looks fantastic. So much more portable as a self contained unit with the transducer incorporated into the throne and the power supply and switching all streamlined in a nice little flight case.
GO GET ONE (or two)
Thanks again Bermuda!