what do you meay "stronger blade"? longer edge retention, more tolerant of prying, or something else?
There are, of course, VG10 and S30V, both of which are better than 440C. Actually, you can add 154CM to that list, although I'm not terribly partial to that material.
The first knife that comes to my mind is a Spyderco Native, with either VG10 (Native 3) or S30V (Native FRN).
That said, the 550 has a legion of fans and lots of support. The steel is not flashy, but it's actually pretty good.