I have a Sony STRE597 AMP, I understood it was a 6.1 surrond sound, but from what I read Dolby Prologic IIx is 6.1 and 7.1. The sony is only Prologic II. the manual indicates its DTS Neo 6 ?? It has a centre rear speacker so am now confused ?? whats the deal with 5.1 6.1 and 7.1, every DVD i buy seems to be 5.1 anyway. What use is this Neo 6 ?