Basically, if you register your phone as stolen your network should lock down your phone's IMEI number so it cannot be used, even with a different SIM card. They should share this information with all the other phone networks so the phone should be basically useless.
If somebody puts a new SIM card into the stolen phone and tries to connect to their network, the fact that the phone is stolen should be logged with the network. It could technically be possible to find the person who now has the phone, but the phone company wouldn't pursue it and it would be very unlikely that you could convince the police to pursue it.
So, with the IMEI number you can make your phone useless, but you won't be able to track it down.