7x50 are all you need. The 50 aperture will give you enough light for poor conditions, a 35 aperture is all you need for sunny days.
Most of the 7x50s you'll see are porro prism design, and susceptable to knocks putting them out of alignment. Cheap or expensive, drop them and they're into the shop. The roof prism binoculars are much more sturdy, and I have an 8x35 roof prism set that's taken a beating for years with no change in alignment.
If you really need more power, you have to go image stabilization. I've used Larry-DH's Canon set, and much prefer them the the other set I've tried (Nikon?). But, big bucks. Also, I have not idea how rugged they are.