Guidance for powerd and new CPUs

I've gotten three machines in the past few months (all returned) which didn't work with the latest FreeBSD and powerd. I'm trying to find fanless a low-power system for a firewall box that I can lower the speed on in order to drop the power/temp/etc. even more. Ideally it would use like 5W and run cool to warm to the touch--a heat sink is okay but not if it runs at 100F and draws 30W when idle. It's not going to do much most of the time, but it will be powered on all the time.

Unfortunately all the machines I've tried lately have not been supported by powerd or FreeBSD (no cpufreq support in the kernel, or something). Either the CPUs don't have C states or multiple frequencies don't show up or they do show up but they simply don't work or they show up and seem to work but don't affect heat or power usage...

Is there any way to determine if the chip supports this stuff before I buy it? Or does anyone have recommendations that they know work for this purpose?

(I did try a EdgeRouter, but it was a big pain to deal with, so I sent that back also.)
Without support for hardware offloading the EdgeRouter Lite is just a curious MIPS64 board. It has working FreeBSD support, but the real power of the octeon platform as a router and firewall is in its offloading engines of which FreeBSD supports only the crypto engine.

An APU2C4 board should fulfil your requirements.