Oh, that's better, Chrisnut! As a rule of thumb you can run 5 sheep per acre, so 1 1/2 acres will be fine for a couple of sheep and their lambs (if they're not sharing it with 4 pigs!)
Re: x-breed vs pure breed, depends on the breed, rather.
Another consideration is what tup you can get the use of. If you'd send your ewes to your local farmer to tup for you, or if he'd lend you a tup lamb to use each year, then you need to choose sheep that will manage to lamb lambs of that type
.
Do you have any breeds or types of sheep in mind? Are there some that you like the look of?