We have product called the LANGuardian which integrates with a number of Solarwinds modules including SAM. It captures and analyses traffic using Deep Packet Inspection and because it uses DPI and looks at packet contents, it can give you a lot of detail and visibility into network and user activity across your network including server bandwidth usage, down to the bandwidth used by transactions between servers and between servers and users.
You do need Netflow, just passively sniff some traffic at any point in your network, usually via a SPAN port or TAP. If the servers you would like to monitor are connected to managed switch which has a SPAN port available, you can download a 30 day free trial, deploy on Vmware or a standard server and start collecting data. It captures all activity to and from each server and stores it in a built in database, absolutely no performance impact on your Solarwinds implementation.
It can be used to monitor and trend the traffic to and from each server, the bandwidth usage of each server, if it is a file server for example, the user names and IP addresses accessing the files, the file names, the sizes of those files, date and time, the servers consuming most bandwidth, least busy, etc.
Short video of the integration here
