I have tried so many different brands. Unless you want a top sheet that is too small and pillow cases that don't cover the whole pillow, you might have to buy everything separately, rather than a set. So if you have a queen, buy the queen bottom sheet, but then buy a king for the top.
If you buy really high thread count sheets that aren't so expensive, the manufacturer makes up his cost by cutting off some of the width or length or both. Then sometimes they shrink in the wash.
Otherwise, for a soft sheet, that will fit properly, you will have to go pretty expensive. The only one I've found that actually fits in every way is my Steve Madden sheet set from JCPenny, and they are usually on sale and you can get a pretty good deal on them. It isn't so soft as I'd like, but after I've had it for a while, I think it will soften up a bit.