Hi James
You can use 1 ASIO host for each soundcard, (Or 2 if you add ASIO4all) thus with one soundcard you can run 2 standalone VSTi.
By adding the Jack program you can use multiple standalone applications simultaneously with just the one ASIO host. (Hence AFG’s exciting moment is easily achievable with Windows)
The ASIO specification only allows for one host, however by using Jack, you get the same performance as if it allowed multiple ASIO.
If you look on the MS Jack screen you will find only one Mediastation output, the others are for connecting directly to other VSTi. (It may look like dedicated multiple ASIO hosts/driver’s (Particularly the way they are named) however there is in fact only one)
Note: The layout looks exactly the same in Windows.

Energy XT and Console are VST Hosts which can be used standalone, or can be used as a plug-in, thus expanding the capabilities of the standard VST Host.
Example using OAS: If I load Kontakt into slot 1, all I can use is Kontakt, (I have to use another slot if I want to use another VSTi)
If I load Energy XT or Console into slot 1, I can then load multiple VSTi into energy XT or Console, (As they are hosts) and access them all using just slot 1. (Leaving the other slots free for other VSTi or other instances of Energy XT/Console)
Hope this makes things clearer

Bill