An APU for a graphics-heavy computer like a HTPC? I've never built one, so I wouldn't really know, but it logically seems like you need a nice graphics card, no?
The only reason to have a nice graphics card on an HTPC is if it's intended for gaming. Normally they're intended for video playback, and even the lowest end CPU and CPU can do that decently. APU's can work out well even for low end gaming (even hardcore gaming, but you'd have to use low quality settings).