I don't use Cubase, so other have to help. But I really think one problem to your latency lies in the ASIO drivers. I'm confused. You mentioned that you are using Creative Audigy soundcard - why then do you use Realtek drivers, and for that matter, use Asio4all? Audigy should have their own ASIO drivers.
Do you have 2 soundcards? I don't understand why Realtek drivers are there. If you have 2 soundcards, you really should disable one of them.
I'm not sure of Audigy supports duplex mode. Anyway, that shouldn't affect the latency of your VSTi.
Also note that most pro soundcards also have buffer settings. Sorry, I don't use Audigy so I can't help you there again.
My suggestion is still to try to make sure you are using the Audigy's inherent ASIO drivers, uninstall ASIO4all (may interfere with Audigy's ASIO), disable other soundcards (may also interfere). If that doesn't work, make sure you have your Cubase installed in a dedicated boot partition with nothing else installed. If you have not already done so, you should. Once you have a clean installation, things will work smoother...and faster.