One of your specs was "grows tall two-stories". Is the master bedroom you're wanting privacy for on the second floor of the house?

If so, you might want to find a way to appreciate the acacias.... To get a tree planted that would block the second floor over the next few years, it might very well take many thousands of dollars.

There are others that could be planted to replace the acacia, for a more reasonable cost, but you might have to wait 10 or 20 years, minimum, to get privacy on the second floor.

Linda is right - trees don't grow overnight, so consider carefully before removing and replacing. Does space allow you to put in more trees? If so, you can plant some new ones and let them grow in before you remove the Acacias. Screening does not have to be ON the property line, and 50 feet is a lot of space. You could fit a staggered tree screen in there that can be renewed on a staggered schedule without having an intervening moonscape! It can include evergreens but need not be limited to them.

What you need to do is to cruise local nurseries and see what kind of trees they have. Read about those varieties before buying. You could also ask for suggestions on the tree forum, but really, will you buy anything you can't get locally? In that case, you might as well see what you've got available first.

KarinL