Just for the record, I've begun to conclude that even the OP is "better off" than am I. OP opted to use a dedicated HT - PC. I had always followed a strategy of making my systems "general purpose." Call me nuts -- I dunno . . .
I will promote this advice most emphatically and profoundly, though.
Once you have either the HTPC or "HT-capable-PC" configured for anything related to HDCP, high-def video, display -- even sound -- and you're sure all the drivers are working tip-top, you will update those drivers at your own risk of another spate of frustration and extra work.
If you want HD TV, then plan the hardware to cover those bases. I've variously used Display-port-to-HDMI cables, DVI-to-HDMI cables, and HDMI-to-HDMI cables. I advise you prepare yourself for the simplest, easiest connection with the greatest chance of total success: HDMI-to-HDMI.
Beyond that, with the right components, you can use the WMC plug-in audio-renderer-updater to switch WMC between speaker systems with little trouble. But if you're going to really "do" this -- you'll have to choose your channels based on what's available for the display. It's one thing to have an "HTPC," but another to provide some modicum of LiveTV to several of "any-old-computers" in the house. For this, your cable-provider offers up digital channels which are not "HD."
"Stuttering" is probably a failure with more than one possible cause.
After all this blather above, I'll hold off reciting my own opinion about the extensive troubleshooting you could do with something like this. It took me more than a week or two just to get my first "HT-capable-PC" working right with cable-card, HDHR, AVR and HDTV. Only this week have I totally perfected it after three or more years of higher-than-necessary maintenance.
So why is WMC "orphaned?" Why has XBMC become "Kodi," and SageTV has been absorbed by Google?
Because the time-constrained herd calls the shots in the marketplace.
That's why.