Thanks for the many inputs.
Meanwhile I tried several things and found out some things.
1. Removed all external harddrives, optical drives, card readers etc. -->> problem still there
2. Tried to check and repair permissons of the harddrive. Seems that there were several (over 100) errors for permissions with iTunes and Safari. As far as I remember these were indeed the last two I updated, but I saw no relationship to the problem. Repairing permissions did not work. After performing the repair three times and re-check, all stay the same.
3. Looked at the results in the console. This is what it showed me:
4. Copy pasted the results from etrecheck:
EtreCheck version: 1.9.11 (43) - report generated 29. Mai 2014 11:08:18 MESZ
Hardware Information:
iMac (27-inch, Late 2012)
iMac - model: iMac13,2
1 3.4 GHz Intel Core i7 CPU: 4 cores
16 GB RAM
Video Information:
NVIDIA GeForce GTX 680MX - VRAM: 2048 MB
System Software:
OS X 10.8.5 (12F45) - Uptime: 0 days 0:13:22
Disk Information:
APPLE HDD ST1000DM003 disk0 : (1 TB)
disk0s1 (disk0s1) <not mounted>: 209,7 MB
Macintosh HD (disk0s2) / [Startup]: 999,35 GB (202,25 GB free)
Recovery HD (disk0s3) <not mounted>: 650 MB
USB Information:
Apple, Inc. Keyboard Hub
Logitech USB Optical Mouse
Apple Inc. Apple Keyboard
Apple Inc. FaceTime HD Camera (Built-in)
Apple Inc. BRCM20702 Hub
Apple Inc. Bluetooth USB Host Controller
Thunderbolt Information:
Apple Inc. thunderbolt_bus
Apple Inc. Thunderbolt to Gigabit Ethernet Adapter
Gatekeeper:
Anywhere
Kernel Extensions:
[not loaded] com.Belcarra.iokit.USBLAN_netpart (2.0.2) Support
[not loaded] com.Belcarra.iokit.USBLAN_usbpart (2.0.2) Support
[kext loaded] com.Cycling74.driver.Soundflower (1.6.6 - SDK 10.6) Support
[not loaded] com.RemoteControl.USBLAN.panther (1.6.1) Support
[not loaded] com.RemoteControl.USBLAN.usbpart (2.0.6) Support
[not loaded] com.belcarra.iokit.netpart.panther (1.6.1) Support
[not loaded] com.belcarra.iokit.usbpart.panther (1.6.1) Support
[kext loaded] com.nvidia.CUDA (1.1.0) Support
Startup Items:
CUDA: Path: /System/Library/StartupItems/CUDA
Launch Daemons:
[loaded] com.adobe.fpsaud.plist Support
[loaded] com.adobe.SwitchBoard.plist Support
[loaded] com.marketcircle.billingspro.configd.plist Support
[loaded] com.marketcircle.daylite.accessd.plist Support
[loaded] com.marketcircle.daylite.attachmentd.plist Support
[loaded] com.marketcircle.daylite.backupd.plist Support
[running] com.marketcircle.daylite.cardcald.plist Support
[running] com.marketcircle.daylite.portsd.plist Support
[loaded] com.marketcircle.daylite.staged.plist Support
[loaded] com.marketcircle.daylite.touchd.plist Support
[loaded] com.microsoft.office.licensing.helper.plist Support
[loaded] com.oracle.java.Helper-Tool.plist Support
[loaded] com.oracle.java.JavaUpdateHelper.plist Support
[not loaded] com.teamviewer.teamviewer_service.plist Support
Launch Agents:
[not loaded] com.adobe.AAM.Updater-1.0.plist Support
[running] com.adobe.AdobeCreativeCloud.plist Support
[loaded] com.adobe.CS5ServiceManager.plist Support
[loaded] com.nvidia.CUDASoftwareUpdate.plist Support
[loaded] com.oracle.java.Java-Updater.plist Support
[not loaded] com.teamviewer.teamviewer.plist Support
[not loaded] com.teamviewer.teamviewer_desktop.plist Support
User Launch Agents:
[loaded] com.adobe.AAM.Updater-1.0.plist Support
[loaded] com.adobe.ARM.[...].plist Support
[loaded] com.adobe.ARM.[...].plist Support
[loaded] com.google.keystone.agent.plist Support
[running] com.spotify.webhelper.plist Support
[failed] com.taoeffect.EspionageHelper.plist Support
User Login Items:
Dropbox
Internet Plug-ins:
AdobeAAMDetect: Version: AdobeAAMDetect 2.0.0.0 - SDK 10.7 Support
FlashPlayer-10.6: Version: 13.0.0.214 - SDK 10.6 Support
QuickTime Plugin: Version: 7.7.1
AdobePDFViewerNPAPI: Version: 11.0.07 - SDK 10.6 Support
AdobePDFViewer: Version: 11.0.07 - SDK 10.6 Support
Flash Player: Version: 13.0.0.214 - SDK 10.6 Support
SharePointBrowserPlugin: Version: 14.1.0 Support
Silverlight: Version: 5.1.20125.0 - SDK 10.6 Support
JavaAppletPlugin: Version: Java 7 Update 55 Check version
Safari Extensions:
Open in Internet Explorer: Version: 1.0
Audio Plug-ins:
AirPlay: Version: 1.7 - SDK 10.8
iSightAudio: Version: 7.7.1 - SDK 10.8
iTunes Plug-ins:
Quartz Composer Visualizer: Version: 1.4 - SDK 10.8
User Internet Plug-ins:
Google Earth Web Plug-in: Version: 7.1 Support
3rd Party Preference Panes:
CUDA Preferences Support
Flash Player Support
Java Support
Perian Support
Time Machine:
Time Machine not configured!
Top Processes by CPU:
6% mds
1% WindowServer
0% fontd
0% Creative Cloud
0% ocspd
Top Processes by Memory:
328 MB firefox
147 MB mds
115 MB WindowServer
82 MB Finder
82 MB Dropbox
Virtual Memory Information:
12.98 GB Free RAM
1.37 GB Active RAM
299 MB Inactive RAM
1.35 GB Wired RAM
354 MB Page-ins
0 B Page-outs
5. Activity monitor shows no special use of CPU while spinning wheel. It only shows that the finder is not responding in RED for the 20 seconds.
All other applications work like expected during spining wheel. No slow down there.