Right...you should be able to get that really low on teh latency side.
I'm very rusty with VST 5.1......everything changed in SX! And I use Logic and ProTools...
Make sure you've got one driver only loaded. Make sure that the EMU mixer is setup default, no in/out routing. The EMU mixer is really powerful, but it's best to let Cubase handle the monitoring fo now. Ifyou have some monitoring setup on the EMU mixer, and have selected software monitoring in cubase that will cause some strange things...
Are you using an external mixer too?