An HT receiver is a good way to do this. You don't need a three chanel amp this way. Make sure the receiver also has inputs and outputs for the main channels.
I have a 2 channel set up. What is the best way
I have a REGA Mira 2000 integrated amp and what to get into surround sound. I am running B&W 602 as my main speakers. I have a center channel speaker and surrounds. Could I purchase a A/V received and hook it up with my integrated amp? In other words, would it work if my integrated amp ran the main speakers and a A/V reciever ran the center/surround speakers? I want to leave my main speakers hooked up to my integrated amp. What are some other possibilities?