I don't play any PC games at all and I've been clocking the XP Barton 2500 at around 3600 so I'm not too concern about cpu usage, though the 5.1 is much improved over 7.1 in this regard and aim more toward gamers, it's not as cpu intensive and has a better DAC, and work with Window's proprietary volume control.
My Stereo receiver doesn't has any DAC so the conversion will be depend heavily on the Soundcard. This weekend I'll stop by CompUSA or Microcenter and get the EMU 0404, it sports a Burr Brown PCM1804 ADC, and AKM AK4395 DAC, spec on these chips are very impressive!! this should be a good candidate to compete with the Revo 5.1.