Currently, I use HWMonitor and Speccy. Honestly, HWMonitor is hideous to look at and is too busy for my liking.
HWinfo brings in tons of pertinent info.
MSI Afterburner will still work even if you don't have any MSI components installed. It's a good monitoring software.
Aida64 is probably the granddaddy of them all.
I use Afterburner to control my GPU's fan speed, didn't know it was a monitoring software as well. I'll give HWInfo a shot and couple that with Speccy. I've read AIDA is not free.
No Aida64 is not free, but in my book, it's worth the price. At least it was for me.