Hm. Well, Dolphin is a very CPU-heavy program, and I would assume any current "standard" Dolphin build would have at least an i5-2500 processor running at stock speeds (or overclocking, if using a 2500K). Could you post the specs of your new PC? What kind of CPU/GPU are you planning on using?
Wind Waker is a popular game for emulation; I'm certain there are folks out there who will have tried it with whatever setup you're planning and have posted the results somewhere. I would imagine the game would be playable (in HD), but I'm not sure about the framerate.
Edit:
Here is a video of the game running in 30 FPS with a 955 BE (like in the guide's 'very good' build) and a less powerful video card. I don't know Spanish, so I can't tell if the author is saying it's running in 720p or 1080p, but it's in HD nonetheless.