Well, I ordered a fan controller from NCIX.com on Thursday, and got in on Friday (wow). I went with a
Scyth Kaze Master Ace, 5.25 inch bay version. I had tried the NZXT Sentry 2 before for use with my HAF922 and using it made my fans buzz and drone, completely negating the point of a fan controller, supposedly a common problem with that piece of shit hardware.
But the Scyth controller, connected to all 3 of my stock HAF922 fans, works like a charm. No extra noise at all, can see the fan RPM instead of just a percentage, it's perfect. I spent like 3 hours yesterday redoing all of my cabling in my case to make it as neat as possible when installing the controller, so I'm very happy with the inside of my computer now. The loudest thing now is my Hyper 212+ fan, going to consider looking into a quiet replacement for it sometime I think.
Anyway, the Kaze makes my HAF922 fans pretty much silent at 540 RPM for the front and top fan, and 960 RPM for the back, down from 700 RPM and 1200 RPM respectively. And the lower air flow doesn't really affect CPU temps much at all. Idle is more or less the same, though maybe a lower min temp at full blast, and at load, it's pretty similar, maybe a degree or two hotter with lowered speeds. Of course, when I don't need silence, I can just turn the fans to max again.
Overall, strongly recommend the Kaze controller for any HAF922 owner who wants to make their case quieter.