Yes, you can deactivate Top Sites and Cover Flow like this:
Quit Safari if it's running and open System Preferences>Network>Advanced.
In the DNS Server tab, make sure IPv6 is turned off, and enter these two DNS servers to replace the ones you currently have:
208.67.222.222
208.67.220.220
click Apply Now and quit System Preferences.
Next, do these things in order:
1. Go to Home/Library/Cookies and delete the Cookies.plist file.
2. Go to Home/Library/Caches/com.apple.Safari and delete the contents of that folder.
3. Go to Home/Library/Caches/com.apple.Safari/Web Page Previews and delete the contents of that folder.
4. If you
don't want to use the Top Sites feature, open Terminal and paste in this command:
defaults write com.apple.Safari DebugSnapshotsUpdatePolicy -int 2
5. Go to Home/Library/Caches/Metadata/Safari and delete the contents of that folder.
6. Go to Home/Library/Caches/Safari and delete the contents of that folder.
7. Go to Home/Library/Safari and delete these files (if you have them):
Downloads.plist
History.plist
Form Values
LastSession.plist
WebpageIcons.db
Then Repair Disk Permissions, restart Safari and see if the speed is improved.