I have two PhotoClam ballheads that I purchased via Really Big Cameras. I have the PC-36 and the PC-48. I put the 48 on a set of Gitzo alloy series 3 legs and the 36 on the Manfrotto 055MF3 magfibre.
I like the side button on the shoe that drops the safety pin to let me slide the lens or camera plate into the shoe without having to open the shoe too far. I also really like how both perform after being cold soaked at sub zero temperatures for hours.
The Manfrotto legs are only used with short focal length lenses. The Gitzo legs are used up to 300mm tele although I could go a bit more if pressed. I have a set of Gitzo series 4 alloy legs I use for the really long focal lengths.
I would go with the PC-36 as the minimum. It works well and is reasonably priced and will be a good match if you upgrade your tripod legs to something more sturdy.
You may also want to compare pricing between your linked site and Really Big Cameras.