Are you trying to transcode with servio? If so the CPU might be your issue I have an amd 250u 1.8ghz DC that works fine in my htpc with a 5450 but the video card takes care of most of the work. In your case I don't think video is doing much of anything.
Yeah doesn't sound like your vid card is helping at all. I have an HTPC with probably a fairly equivalent vid card and C2D E6300 and I get ~5% CPU usage playing BD's. Check the setting in the software to see if 'hardware acceleration' or some similarly names setting is enabled.