looking for a tool...

Hello, I was wondering if anyone could point me in the direction of a tool capable of sniffing (or reading pcap files), and reporting on lan station thruput in terms of bits per second. Ideally I'd like to be able to generate a sorted report of the top users and top thruputs observed and so forth. The traffic is pppoe and I need to monitor it at a specific switchport where I can arrange span. Thank you.