D3D is DX11. It was just generically named so it doesn't have to be changed every time the devs bump a DX revision. DX9 was dropped since it doesn't replicate all features that are needed. DX11 = D3D in the latest version.
If you're still getting poor performance, try reducing IR to 1x. If framerate goes up, it's a GPU constraint. If it doesn't, it's your CPU (not that you can make it much faster than 4.5GHz).
I'm not familiar with any speed enhancements for MP3. Maybe someone else here can chime in with that.
https://wiki.dolphin-emu.org/index.php?title=Metroid_Prime_3:_Corruption_(Metroid_Prime:_Trilogy)
This looks potentially relevant: https://code.google.com/p/dolphin-emu/issues/detail?id=5185
If you're still getting poor performance, try reducing IR to 1x. If framerate goes up, it's a GPU constraint. If it doesn't, it's your CPU (not that you can make it much faster than 4.5GHz).
I'm not familiar with any speed enhancements for MP3. Maybe someone else here can chime in with that.
https://wiki.dolphin-emu.org/index.php?title=Metroid_Prime_3:_Corruption_(Metroid_Prime:_Trilogy)
This looks potentially relevant: https://code.google.com/p/dolphin-emu/issues/detail?id=5185