E4200v1 - Monitor Home Network / Internet Bandwidth?

I'm wondering if there is an easy way to monitor how much bandwidth is being consumed at any given moment for a home network.specifically, for the incoming/outgoing internet connection.My network is as thus:

DSL Modem -> Wifi Router (Linksys E4200v1 - PPPoE enabled here) -> Gigabit switch -> 2nd Wifi router (D-Link DIR-815 - DHCP disabled, repeats same SSID and password)

Most devices are connected directly into the switch, with one computer hard-plugged into the DIR-815 (I will eventually change this, as the 815 only has 10/100 ports).Basically, I want to easily be able to check how much up/down data is being sent for my internet connection. This means that I cannot use a program on a computer (I've used DL Meter before. Works great, but limited to a single computer).

The Linksys E4200v1 is using standard firmware, but I'm not opposed to loading DD-WRT onto it (was the original plan anyway, just never got around to it), if DD-WRT has this capability.Nice to have feature: Ability to see which devices are consuming what part of the bandwidth. Not necessary, but would be a cool feature.Alternatively, if there is a cheap (like $100 or less deal) box that can interface, say, between the E4200 and the switch, that can do this, that would work as well.