Though what I've never been a fan of are the all-in-one manufacturer specific system monitoring tools, and that's why you won't find me recommending any here today.

HWMonitor is fast, simple, logs all the information you could need out of it, and keeps track of every PC vital stat you could reasonably be after. That helps when you're doing some actively to the system and wish to monitor the impact those changes have in real-time. While it's effectively more of the same by way of monitoring, the handy GPU overclocking tools and live graph presentation really aid in easily understanding the monitoring data presented to you over time. I'd also like to give an honourable mention to the old hand that is MSI's Afterburner software.

The built-in tools Performance tab offers a lot of data nowadays without the need for any third-party tools, and it'll even report your graphics card's temperature. Another system monitoring tool worth mentioning, and in keeping with the spirit of minimal fuss, is Windows' own Task Manager.

Msi afterburner power monitoring