The need for more robust hardware is always a struggle. Cisco hardware is very exspensive so you always want to do more with it than you origianlly intended. What seems to always end up happening for me is that I load the IOS with just the features that I need and then later I need to a feature that isn’t in that version of the IOS. The question is always “Which version of the IOS does what I need it to do”?
Now there is a tool that will allow you to compare the features of the different flavours of Cisco IOS. The Cisco Feature Navigator FAQ found here allows you to compare and contrast different flavours of different of the same version of the IOS or different versions of the same flavour. It is a tool worth checking out.