I saw a deal on craigslist for some 4th generation Klipsch Reference RF-52 front speakers for $385. After looking at some pictures and emailing the guy, the speakers seem to be in almost perfect condition. Another question I have though, is there any audible difference at all between the 4th and 5th generation of this speaker? I didn't realize that it was the 4th generation until getting serious about buying it and now I'm a little worried. Also, would upgrading to these speakers, along with buying the Reference RC-52 center channel as well, be worth the upgrade from some Polk Audio TSi300's front speakers and CS10 center channel? My subwoofer is the Klipsch RW-12D.