Get better hardware and overclock, that's all you can do for SMG1/SMG2, really. Both SMG1/SMG2 are very CPU intensive due to all the data that is being processed such as vertex data and some areas/levels/galaxies are more CPU heavy than others.
I just bought a Core i7, 6 GB DDR3 (Tri-Channel) Ram, 2 Nvidia Geforce GTX 460's and overclocked to 4.2 Ghz. I'm now getting between 55 FPS - 60 FPS constantly even in heavy galaxies and the observatory.
Another thing, you can keep HT enabled while playing Dolphin, just disable "Lock threads to cores" as this is bad for any HT processor since it will lock the threads to one physical core and one virtual core decreasing performance.
I just bought a Core i7, 6 GB DDR3 (Tri-Channel) Ram, 2 Nvidia Geforce GTX 460's and overclocked to 4.2 Ghz. I'm now getting between 55 FPS - 60 FPS constantly even in heavy galaxies and the observatory.
Another thing, you can keep HT enabled while playing Dolphin, just disable "Lock threads to cores" as this is bad for any HT processor since it will lock the threads to one physical core and one virtual core decreasing performance.