As long as they are entirely different sound cards, or sound cards designed to be grouped together, you should be OK. You or more likely Windows will determine one to be default and the other one will be ignored unless you specify to use it from an application example right click on win amp, select options/preferences/plug ins/output/direct sound output/ and click configure, there you should see all available sound output devices.
As far as patching, you'll have to prolly hard wire one into the other. I have the SPDIF output of my 8 channel card hard patched to the SPDIF input of my default stereo card. As for making 2 stereo cards into a 4 track config, it ain't gonna happen. If both cards are the same, they will walk all over each other.
Good luck with your endevor. You are treading on some tricky ground here.