As mentioned in the comments, you need to convert the analogue video into a digital stream before you can use it either with the Surveillance Station or simply to store it to hard drive.
Synology publish a list of supported video servers for Surveillance Station I believe and they include the Axis range and at least some from Vivotek.
To handle 8 analogue streams will always require something special as that is a lot of data that has to be handled and converted.