I am a sophomore in college majoring in network security. I am hoping to finish up my CCNA and then sit for the CCNA:Security exam. I have funds available to purchase a home lab for my studies but I would like to save as much money as possible since I'm a poor starving college student.

I'm getting the impression that I will need to buy the following:
Two Cisco 2620XM 128/32 12.4 Routers
One Cisco 2611XM dual Etherent 128/32 12.4 Router
Three Cisco 2950 Switches
I perfectly agree with buying (3) 2950 switches but I'm hesitant to spend so much money on the routers. Do I really need to have (3) SDM capable routers in my lab or could I just buy one router that has enough memory to run SDM? I've decided to go with all XM's because they run IOS 12.4. I plan to eventually work towards CCNP so I'd hate to buy equipment now that will be useless when I need a lab for CCNP. Any thoughts would be appreciated.