|Rockwell Collins Amplifier|
On Ebay you will find a wide variety of Vintage Ham Radio Amplifiers. There are the common names such as drake, ameritron and siltronix as well as many other excellent amplifiers. Now there are other amplifiers that are built by someone and may not be approved by the FCC. Another amplifier that is not approved in the United States, but is okay in other places are the RM Italy Amplifiers. I have read some good and not so good reviews on them. They seem to be somewhat fairly priced for people to afford. Just make sure of the power the amplifier puts out and make sure it will function with the ham bands you are planning on transmitting on.
Another important point to look for when purchasing an amplifier or any Ham Radio Equipment off Ebay is whether or not there is a warranty period or return policy. I have heard of stories when someone bought something and there was a problem with it. Unfortunately there wasn't any warranty or return policy, so the person was stuck with a useless piece of junk. Now you can buy some new items through Ebay, most of the time the item may be used. If you specifically want to buy new equipment I would look at Universal Radio, Ham Radio Outlet or DX Engineering. There are other resellers on the internet with good deals, but remember to check out any reviews before purchasing.