I've heard tons of good things about mountain horse. In fact I just got back from the barn and someone was mentioning how much she loved her pair. Once I have my funds together if I haven't found a pair by then, I may just have to take you up on that offer. Boots are so expensive but the ones you posted seem doable, especially if they last like you say.
I have a great pair of Vogel field boots for sale that fit your measurements perfectly! They are size 7 1/2 and half a calf height of 18" so there is an inch extra for the crease at the ankle when you are riding. These are used custom boots so you can send them to Vogel for alterations to either let out the calf or have them made smaller if they stretch out. I evented in them and they are super comfortable and still have years of use left in them. I would stick with the leather ones because they are able to be altered and the rubber ones are not. The rubber ones are also terribly hot in the summer!