The type usage you're planning on should determine how much $$ you should spend or plan on spending IMHO. If you simply need something for checking out movement or a couple of deer that show up in the back 40, any decent glass will likely work. But, if you're out west using the glasses for hours on end glassing, I can promise you you'd rather have the best you can afford to avoid eyestrain.
I'd agree that 8X32 or 8X40s are perhaps the most useful sizes in most cases, but if longer ranges are involved 9X40 or even 10X40/42/45 can be an excellent choice as well. As with rifle scopes, better glass and coating will make for better clarity and low light performance. I've never heard anyone say they wished they had spent less on a scope or binoculars....:no: