using other vsti's on a virus track?

[Crossfire]

In Virus Control go to the config page and change the output from USB1 to USB2 or 3.

Then create another audio track in Ableton. For the input of this new track select Virus then in the 'secondary' drop down box for the input select Virus2/3 depending on the USB channel you set above.

So basically all you've done is move the output of the virus for that part from the main Virus channel to another one for separate processing.

Also you can use the analogue outs routed back into your sound card and setup new audio tracks in Ableton to receive these. However this introduces some latency which can be fixed manually using pre-delay settings in Live.