I am happy with my Arca-Swiss d4 also a significant investment (~$1100). That being said I am also happy with my SunwayFoto GH-PRO II Geared Head ($225). I use the Arca on my tripod and my SunwayFoto on a custom car window mount. Hardly use the tripod anymore but use the window mount heavily (can not walk well and confined to car for most photos). If I had to do it over I would just get the Sunway. It seems robust enough with smooth operation.
I also have a Manfrotto 410, too large and heavy. Plus a Benro which seems clumsy, not as well made, and overly large compared to the SunwayFoto for about the same price.
Just noted a new post about the D4. One advantage it has is that if you release the gearing you can move the camera about similar to being on a ball head. Nice but I don't use because if I am doing that kind of work I use a tripod with an AcraTech ball head and that works better.
For rapid, large movements the D4 has a lever system which is very nice. The Manfrotto and Benro have coaxial release knobs which hurt my fingers and seems awkward. The Sunway, while not elegant, just uses a flip out handle which works well.
In any case I would mount the head on a AcraTech leveling base. I have tried a bunch of those also and this is the best.
If you are the Leica type and have to have the very best regardless of cost, get an Arca. If you are more practical with your money, the SunwayFoto fills the bill for 25% of the cost with 95% of the goodies.
As you can tell I like geared heads. The SunwayFoto was a gamble because it was not advertised widely and at the time I did not find out much about it on the net. I don't know about the RRS plates cause I use cheaper alternatives and they and my L-brackets work fine.
Note that only the Manfrotto has a geared pan. I thought I would miss it but I do not. Once you have the other controls as you like the pan on the SunwayFoto is slightly dampened and very smooth so precise control is easy. I use is frequently for panos.