Hi
I do not think this information exists due to the extrem complexity of it.
and are you shure you want maximum ? normally one would want minimum or expected performance.
http://www.cisco.com/web/partners/downloads/765/tools/quickreference/routerperformance.pdf
This document tells you what the 1841 and 3825 router can route (MINIMUM)
1841
75 Kpps and rated for 38.40 Mbps through it.
The 3825
350 Kpps and is rated for 179.20 Mbps through it.
When you add different types of feature sets it will bog down the router dependant on how much it routes of each and how many features you enable and what type and what size is the packets and so on.
Good luck
HTH