Hi
It depends on what type of VIC cards you would like to install.
For instance the VIC-2FXS will not work in the 2800 series, but the VIC2-2FXS will.
http://www.cisco.com/warp/public/765/tools/quickreference/routermodxref.pdf
I have attached a compatability matrix which I hope helps. If it does, please could you rate this post?
Martin