Cisco router for educational purposes

While it might be fun to mess around with a Cisco router on your home network (I totally understand that!) I wouldn't recommend it from a learning point of view. Your scenario is going to be too tiny to explore any of the more advanced functionality of the router, which leaves you with basic port configuration, and that you can learn on almost any hardware.

For your learning needs I would recommend Dynagen/Dynamips http://www.dynagen.org/ which lets you emulate modern Cisco versions. It lets you create topologies that are actually realistic and try out various protocols. If you want to you can connect your emulated environment to your normal network.

If you want physical hardware the Cisco 1800/1900 series (or the similar Juniper J series if you want to learn Juniper) are probably what you should be looking for. But you will be paying a significant premium for a lot of features you have little use for in your home network.

I've purchased Cisco kits from ciscokits.com and have been very happy with them.

How about a Cisco 1841? It's got two built in FastEthernet ports, and it supports WICs so you can practice configuring whatever else, if you want to buy the cards.

It retails for $1,400, but RouterMall has a refurb on sale for $525, and they might knock off that extra $25 if you ask nicely.

A couple of years ago, when I was looking into going for a CCNA, there were very plentiful and cheap 2501 and 2514 routers up on Ebay. If I remember right, they were max $30 each, and had every conceivable feature needed for the first couple of exams. Not that you mentioned exams, but last I knew, they had everything you could need. Bulky and loud, tho, in case that matters.