Experience teaches me that whilst the vast majority of stuff plays nicely with hardware acceleration, don't buy low power hardware and expect it to be future proof or without the occasional issue, as it just won't cope if you decide to do something else, or if your video just doesn't work perfectly with hardware acceleration.
Depends on your priorities though, a low powered graphics card will play MOST stuff out there now fine, with a moderate CPU, but not everything
I'm using some Nexus Real Silent fans (set to about 9v/75% fan speed), Nexus PSU, passive GPU and an i3-2100 running under a Big Shuriken, again running about 50%. Damn near silent, the external hard drive probably makes more noise than the system itself.