Best "pseudo" multi channel from 2 ch sources

As a HT novice I would very much like some guidance as to which AVR's/Processors are known for their ability to make a 2 ch source sound really good at a high end level? I find rear channel added ambiance to be enriching to the listening experience.In my case most of the source material will redbook cds. Also is a center channel speaker imperative for this scenario? Any guidance will be appreciated.