Performance Issues with newest builds

[maximumx2]

Hi @ all !!!

Im always using the newest dolphin builds (currently 6863) x64.
I also always doing a clean new install.

Here's my problem:

Some games can be played very well e.g. Mario Kart Double Dash (GC), Resident Evil 1 (GC), Zelda Twilight Princess (GC), Wii Sports, Wii Resort.

Other games like Metroid Prime Other M (Wii), Donkey Kong Country Returns (Wii), Super Mario Galaxy 1 & 2 (Wii) have huge slowdown independent from what are drawn on screen.

Example: Metroid Prime Other M

A room full with enemies and particle effects ~60 FPS
A room with four walls, a door, no enemies and a switch ~24-30 FPS

I also encounter audio stuttering and hangs during gameplay (mostly wii games).

My Settings:

General:

Enable Dual Core (ON)
Enable Idle Skipping (ON)
Framelimit: Auto (not checked)
JIT or JITIL (JIT, makes no difference)
Lock threads to cores (ON)

Graphics Plugins: (DX9, all other with same settings)

Aspect Ratio: Force 16:9
V-Sync (OFF)
Anisotropic Filtering: 1x
Anti-Aliasing (None - 4xSSAA, makes no difference)
Load Native Mipmaps (ON, makes no difference)
Pixel Lightning (ON, makes no difference)
Force Bi/Trilinear Filtering (OFF)
EFB Scaled Copy (ON)
Pixel Depth (OFF, causes glitches in some games)
3D-Vision (OFF)
EFB-Scale (Integral - Fractional, makes no difference)
EFB CPU Access (ON, makes no difference)
EFB Copy To Texture
Accurate Texture Cache (FAST)

Sound: (DSP-HLE)

Enable HLE Audio (ON)
Enable DTK Music (ON)
Enable Audio Throttle (ON, off makes some cutscenes to fast)
Sample Rate (48,000Hz, makes no difference)
Audio Backend (DSound, makes no difference)
Volume 100%

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My rig:

CPU: AMD Phenom II X6 1090T @ 6x 3.8 GHz
RAM: 8GB Corsair XMS3 DDR3 @ 1333 MHz
GPU: NVidia GeForce GTX 480 (1536 MB)
MB: ASUS Crosshair Formula IV
OS: Windows 7 Ultimate x64

All drivers are up to date and all windows updates are installed.

Hope you guys understand my problem and can give me some help.
Answers and suggestions in german are also appreciated because i usually speak it.

Thanks in advice
maximumx2