What do you want them for? At that maginification, you will need a stand or tripod to support them.
I hunt and consider my equipment to be extrememly important to my success. Nationwide, hunters enjoy a less then ten percent success rate, but those who are in that ten percent, get animals almost every year, and usualy see many before taking one. The reason is because of their knowledge of the animals, the terrrain and the equiment they use.
Just like tooks, there are the cheapy, piece of junk binoculars, the middle of the line that are fine for during the day, in mild temps and clear skies. If what you are looking at will be out in the middle of the day with full sunlight, then you will be happy with most anything under $200.
If you want the most light gathering ability possible, before the sun comes up, and after it sets. If you want to spot a sleeping buck a thousand yards away, under a tree, or if you want to be able to see if the animal is legal or not before spending hours trying to get closer to it, then you really want to spend the money for quality.
The European glass makers have had an edge over their grinding and coating process for decades. Zeiss, Lecia, Swarvarski are as good as you will ever want, or be able to find. They are in the thousand dollar range on up. They are also worth every penny if you are a hunter who is in the mountain four hours before daylight when it's raining and 40 degrees out. You will see more animals. GURANTEED.
The Japanese camera makers have been coming out with some decent optics in the past decade or so. Nikon, Pentax and Olympus are all decent, middle of the range optics. You wont get the same results as the premium optics, but if you only hunt locally, and are not spending ten grand on a hunt to Alaska, or something really severe, you won't be disapointed in them.
Leopold is good, but I wouldn't touch anything else.
10 x 50 will give you the best light gathering ability in a power that you can hold and still tell what you are looking at when it's far away, in low light. Anything more powerful, and you are carrying a lot of extra weight, and not going to see very much out of them.
Be very careful of anything Russian, or cheap. Both are junk and not worth carrying into the field even if you got them for free. If you want to find what you are looking for, don't carry something that doesn't work.
Other factors to consider are the quality of the seals to keep fog out of the glass, the dryness of the Nitrogen and the coatings on the lenses.
Good luck,
Eddie