A receiver has amplifiers built in so that's one worry you can forget about. I'm assuming that you'll be using it as a two channel system, at least for now.
But, when buying used receivers, remember, there's no guaranteee that comes with them like with a new one.
A lot of those are home theatre receiverers and depend on a remote control for many functions which cannot be accomplished without one. Make sure it's included when you buy one or you may never be able to set it up correctly. They can be costly or possibly not even available anymore. A manual is nice, too but most, not all, times one can be found on-line but again, get the manual along with it, aswell asthe remote.
That being said, for a starter system I'd consider any except the Kenwoods and those "unnamed" ones AS LONG AS IT WORKS AND HAS THE REMOTE AND A MANUAL.