The best capture device we recommend is from Epiphan Video;
This capture device works with every ultrasound we have encountered. It is fast and very reliable.
There are some lower price capture devices that will also work;
To stream successfully a PC should have a minimum of 8 gigs of RAM and a Intel i5 or AMD A6 or greater processor. Here is a link to a laptop that would work well for streaming;
The minimum speed of the internet connection should be 10 megs down and 2 megs up.