Let me start with my soap box about sims and lack of hands on training. With a sim you are very limited to what you can do. THey have their place to be sure.. sim'ing ISDN for example is a great idea vs buying the ISDN demostrator at 2k. But, you do not learn the cabling or other parts that are not common like policy routing, wildcard masking and the like.
The 2500s are the workhorse router and run about 500-700 on eBay. The 2514 is dual ethernet which is useful and the 2503 is ether,serial and ISDN. Try to get dual serial ports. The 1600s are great lab machines.. but they seem to run abit higher in price BUT they take up much less room and power. They also have the WIC slot for future use.
I run a 2514, 2503 and a 1601. I use both a couple of DSU/CSUs with a back to back T1 link and a DTE/DCE cable back to back. I also have a 1900 switch so I can have VLANs set up. All were bought used off eBay and one private party. You want no less then 8 meg of FLASH in the big routers.. and no less then a 4 meg flash card in the 1600s. 8 meg flash would be better. 8 meg of ram is plenty for a home lab.
There are virtual labs like Mentor which are great but after 3-4 labs and 80 bucks a pop, you could have bought the router.
The biggest issue is that when you go into the job market as a CCNA or whatever, you are *expected* to know certain things. Without the flexiblity of the real router to load different IOS levels, protocols etc, you have tied your hands. Same goes for the DSU/CSU configs, T1 hook ups, Frame Relay config and so on.
Mike S
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin