I might be wrong but I'm pretty sure that splitter just lets you display the same image on 2 screens, not run 2 screens independently.

The ATI 4850x2 is the only single-card I know of with built-in support for 4 monitors...

http://reviews.cnet.com/graphics-car...-33421567.html

No idea if a 4850x2 will run 4 WoWs on 4 screens with an acceptable frame-rate, though.