My suggestion: Throw Creapative SBlive out the window and get a card with som real ASIO drivers...
Anyway... even on SBlive you should be able to use some ASIO.. so in cubase, go to Options, Audio Setup - System and in the upper right corner of the pop up window, you'll see a place saying "Asio Device"
Right underneath you'll find a text saying "Latency XXX Miliseconds". The number in the XXX field should be as little as possible, try and choose a different ASIO device and see what happens. Usually the best will be the one saying, "ASIO DirectX....."
this might add a little extra.. I'm not too familiar with SBlive 5... but...
Still in the same screen, click on "ASIO Control Panel" and check the top window in the next screen. That's your audio output device. You'll find a small box saying "Buffer Size"... The smaller the Buffer, the shorter Latency, but too little a buffer can cause some serious audio fuckups. So try messing with it.
I have my buffer set to 1024 samples, and it's running with 24 ms latency. It could be smaller, but I don't wanna tempt faith...
hope that helped