"So when I do the 6/12 test, I shouldn't find any movement, correct?"
Correct.
"Assuming I find bad bearings, my follow-up question is, what is a good aftermarket bearing that will have a longer life than the OEM part?"
SKF. Stazi, a CEGer sells them. Read this thread with his info and you can PM him.
http://www.contour.org/ubbthreads/showflat.php?Cat=&Board=wheels&Number=1228967&page=1&view=collapsed&sb=5&o=31&fpart=1
"The car has only 75k miles - way too soon for bearings to go bad, in my opinion."
Depends on the road (or off-road

) conditions.