ahhh, now i can contribute to this... conversation, a word that i use ever so loosely.
as a student at UT @austin, i just transfered out of Mech Eng. to Pure mathematics, and i did a considerable amount of research on the subject.
a PhD in anything inherently involves at least a little research as well as a deep understanding of the subject, so a PhD in most everything will lead to a job @ a university (a professor), since you are overqualified for most everything else
i dont know how many PhD's are awarded each year, but you literally have to advance the field of mathematics and attain a significant amount of international reknown to get a PhD in mathematics in UT
it is important to understand the difference between teaching and being a professor. to teach, you must know how to teach. to be a professor, you must know a lot. the only professors one ever gets to know as an undergrad are the professors that like to/ are good at teaching, but there are many other people in that school who would call themselves a professor but teach only one highly specialized course
well, perhaps that goes for pure mathematics (topology, number theory, etc.) but... well... an applied mathematicians research is much more likely to be commissioned by someone with alot of cash, so... given that i dont know what field of mathematics you are interested in, i would say that you are very likely running into a job in which you would have to conduct research in order to keep food on the table
i could say what little i know about the different fields of mathematics, but it sounds like that isnt what youre interested in here...
you should really see an advisor in the College of Natural Sciences for your university... or contact advisors from different universties if you dont have access to one at yours