If you need it to do surround decoding, then that's a receiver.
If it is just taking the audio signal from RCA or balanced outputs, that's an amp.
Receivers have amplifiers in them, usually quite beefy ones, but not necessarily the most musical ones. You can easily have a reciever doing the decoding and any processing you want, then output to some nice beefy power amps. But thats probably going a little ott
Hope that helps
