This is interesting as the top of page 3 in the manual breaks these "Picture Size" into 2 catagories based upon the interpreted resolution: 480i/480p has Zoom1, Zoom2 modes while the hi-def 720p/1080i/1080p resolutions will have WideFit and Screen Fit modes. Based on this I'd say your TV sees these as 480 resolution devices, which isn't really a surprise. RIGHT-click on your desktop, open Screen Resolution and raise it up to 1280x720 and see how things go. This should allow you to then change the TV to Screen Fit and viola`
Oh... you asked about picking one that looks good: remember, NO DESKTOP will look good once a scaler is in the loop! The sharpest image will always result when the resolution is exactly 1:1 pixel count with the native panel. You're (presumably) hooking your PC to a 47" Plasma display because you want to sit on your sofa and "do" stuff -- NOT because you want a larger display for Excel. You may find that picking 1024x768 from your PC will (most likely) give you the clearest, sharpest display for your Excel spreadsheet, but it may not play well for video playback. BTW, what DO you want to do on this setup? When you mention WMC, it's usually for movies, TV and the such... again, you want to get the desktop showing in full ON THE TV before you ever try WMC. The resolutions CAN'T look "reasonbly well" with the top, bottom & sides cut off... what resolution do you have your video card set to while you're testing this? Which APU model (A4-xxxx, A6-xxxx, A8-xxxx) are you running? Do you have CCC loaded up and running? Which release - 12.xx, 13.xx? Do you have this PC already running on a separate display besides the TV you're trying to use it on, so you know your build is working? HOW do you have the display connected, DVI, VGA or HDMI? Maybe we're missing some basics here... Get that, tell us what worked and then move on to WMC, please.
Samsung saying you need a discrete video card is a load of horse sh!t... The A-series APU is a great core and the video is very nice in the HD6xxx range so don't listen to that hogwash.
We'll get you running... stay tuned :-)