I've found that ordering a couple of 8# jugs of powder, along with at least 5000 primers from Powder Valley is still less expensive than any of my local sources, even including hazmat and shipping. Powder and primers can be shipped in the same container, with only one hazmat charge.
Small rifle primers won't dramatically change your 9mm pressures. One thing going for us 9mm reloaders is that 9mm "standard" brass is the same as 9mm +p brass.
I've only loaded about 25,000 rounds of 9mm using small rifle primers, so I guess I REALLY don't know if they're working yet.