Well, my experience with Dolphin is limited to smash bros. So I'll let someone with more dolphin experience say something. But I will say there are still issues with emulating the wii and some games still don't have 100% compatibility.
If the CPU is the issue, I would wait for the next generation processors and get a quad from that generation. If you are desperate for something right now though, I'd go for the Phenom II 955 and look into overclocking.