Mikeathome1,
I am fairly new to softsynths so I can be corrected by others.
The NI B4 can be used as a stand alone, so you would not need any other software. You don't need a special soundcard. There is a demo available at the NI website, but they really cripple these demos excessively IMO. You could use your Tyros as a MIDI controller. I tried the demo and had some sticky notes I think, but your mileage may vary. A driver update would correct this.
There is also ZR3 and daOrgan, but these are vst which wud require a wrapper and a vst host. Playing an authentic sounding Hammond B3 should make you keep playing, but yea, you will need a computer.
Starkeeper

[This message has been edited by Starkeeper (edited 03-17-2005).]