The expensive video card won't help for video. (I know. . .) The premium video cards are build for gaming and advanced graphics rendering. None work as well as a chip based media adapter with optimized hardware for video playback. The 6150 on board video is about as good as it gets on PC today and its not real good. (The Windows drivers are no better, same problems with tearing, deinterlacing etc.) The best I have seen is from the VIA CX700 Fiirestation, but even then its not perfect.
But I watch it every day with no problem.
Get an Asus M2NPV-VM and use the on board video. Its plenty good enough. Allocate 128 MB for it.
Use an external AV receiver which won't cost much more than the sound card. It will be more fully refined and LMCE can control it. One with a serial interface is the best option for the best control.