Maximum PC

My ISP is starting to crack down on actual download/upload amounts. I only have 40gigs down and have gone over the last 3 months. As a result I'm hoping there is a router on the market that will allow me to set download/upload quantities to specific devices. My network currently has 4 laptops (wireless), 2 desktops (wired), ps3, and xbox 360 (both wireless).

If it is possible I want to be able to set a monthly limit for each device. In addition to this I want to be able to set speed limits (slow them down if they exceed). Is there a router on the market that will allow me to do this? I have a budget of $200.

The Netgear WNDR3700 has the option to set maximum traffic volume(down, or down and up) for the network as a whole, and can also set the maximum uplink bandwidth. It does not look like you can set caps per device on this router.

I know alot of units including smoothwall will allow you to do traffic shaping and QOS but I haven't seen one that will outright cap your data.
smoothwall does have a total bandwidth counter on its main page to help a person keep track of what they are using.
does your ISP have any tools to keep track of your usage? big brother is continuously cracking down on those that don't for obvious reasons.