From a technical perspective, I don't know either. But I've satisfied myself that system load isn't a huge factor by doing a simple test on my own rig. I'll start playing a high-res file with nothing else running on the system, then progressively ramp it up with a variety of menial tasks while continuing to listen. I can discern no differences at all even with everything maxed out and both cores continually pegged at 100%. Not particularly scientific, but good enough for me.