The lowest latency software I know of is called AudioTX communicator. It can be set to run very low latency over network/IP or ISDN but over any digital network, you will NEVER get latency in the area of xx milliseconds, unless you count 500 milliseconds as low latency. In terms of IP STL links, anything under a second is extremely low latency. This buffer is required to keep things reliable, this is the reason webstreams have a long buffer, to give a bit of a safety net.
AudioTX communicator, however is not cheap and requres 2 copies to be licenced (one each end) to form a link. There are cheaper STL solutions out there but this is the most flexible, reliable and lowest latency software solution available, as far as I am aware.
As for 192 mpx, there is absolutely no solution available at present but we are are hopeful that such a program will be forthcoming from this very site sometime.