EMU soundcards use a driver that includes a mixer that can route inputs to outputs. Both in and out may be real (as in jacks on your hardware) or virtual (to connect programs to).  I think you are still stuck with one ASIO client max but I find it quite convenient. You route at will between normal Windows audio clients.

Hardly a general purpose solution but it could be worthwhile to keep in mind when picking a card should you be in the market for one.

Sadly open/free programs like ChucK can't use Rewire and I'm not sure I like Rewire's master-slave architecture.

I hear good things about Reaper, a audio editor that can create virtual devices for routing, it might be worth a look is that would suit your needs.

Yours,
Kas.