Core temp is un supported unless your running a 775 socket, Realtemp is da shiznick!
http://www.techpowerup.com/realtemp/
I've used them all, but -- you're right -- it's important to keep up with the software revisions.
Some folks like to have all the little temp icons in the sys-tray, and those two utilities make that possible. Not bad, since they don't monitor much other than temperatures.
I don't leave those sorts of things running all the time on my systems, though. If I'm tuning or tweaking the system, I like to have "everything" in front of me with one applications: core speeds, voltages, temperatures, fan-speeds . . all of it.
It's important in this business, if you're looking for that sort of utility, that the readings are accurate and jive with other monitor softwares.
For "free," I use HWMonitor. AIDA-64 is great, because it bundles with its own stress-test -- considered to be a "validated" stress-program. But for each PC, you'll pay $25 for a license -- though free to upgrade, I think.
I think, with AIDA, you can get "the little sys-tray" icons through choices in the "View" or other menu. OCCT uses the HWMonitor DLLs -- built-in.
A utility like AfterBurner (for your graphics card(s)) will also track CPU usage and temperatures, verified consistent with other monitoring software. As comprehensive as some of these programs seem, there isn't a single one which offers all the monitoring options you'd want in one application.