This depends on a lot of things, but let's assume for sake of argument that you are running 2800 series routers and thus have a recent IOS image. As long as you have set your bandwidth statements on the interfaces correctly, this should be supported...
I have heard that the J4300 runs at about 70Kpps, and anything besides the 2801 in the 2800 series is at least 120Kpps... note that all numbers are basic IP CEF switching with no extra features... add features like ACLs / Queueing / Shaping / Netflow...
The power supply you are calling "1800W" is really the WS-CAC-1300W supply, but it requires 1800W input because of the inefficiencies in AC->DC power conversion.The Catalyst 6500 datasheet on CCO says that the 1300W power supply is not supported in a...