It all depends upon the number of routes that you are expecting your router to hold. If it is the full Internet routing table (at around 220k) then you would need around 256Meg, if your only looking at around 300 routes then the memory requirement is going to be a lot less a few meg. It also depends on whether the router is running CEF (which I don't know if it is supported or not) again this will increase the amount of memory required.
You could simply load up the 2611 with the routes and see what happens, if it looks like the router is getting overloaded, then you could put a filter list in to restrict the numbers of routes that are learned to those that you need access to.
HTH
Happy Christmas :)
