Hello,
if you are interested in buying a capture card which is able to run several input channels parallel, it is important to buy the right one.
There are many cards in the market which are not able to do this!
Each analog/digital converter chip has only the ability to handle ONE camera!!! There is special software out there, which shows more than one camera for a chip, but only with a trick. The input channel is always periodical changed, so that one camera after the other is showed. But this is not a good way, because the video image has very low quality and the program can't record from all cameras (input channels) parallel.
So you need a card which has so many chips like channels you want to use.
I have got an email from a customer who successful runs such a card.
The ebay links are old, but now you know which kind of card is running well.