Osborne brand are pretty decent, sometimes, but most of the stamp sets i've seen around the planet the last few years are pure excrement!
If you just want a cheap set for stamping stuff that does not matter much, the PA stamps will do, until someone finds some hard material and obliterates the edges and flattens the stamp off the face.
Looking for something nice? Expect to pay rather a lot (well into 3 digits, compared to about $20 from PA), and try to see them first.
A good set of decent hand-cut stamps is a joy to use! I'd love to find a decent set of older style letter and number stamps, but have not run across much worth buying.
Cheers
Trev