Dane- There are a few reasons to consider 7.1 over 6.1.

a) "Reversal". Front-to-back reversal is a psycho-acoustic phenomena whereby if there is a sound directly behind you, the brain *may* construe it to be directly in front of you. Now, with the sight cues that are obviously present with a TV in front of you, this is admittedly rare, but it does occur. 2 rear channels vs just 1 helps to minimize this.

b) People who have had 6.1 and then upgraded to 7.1 (like me for example ), typically find that 2 rears do a better job of filling in the rear soundstage vs just 1.

c) Logic 7, in my opinion, is the best soundfield out there. Logic 7 can be configured for 5.1 or 7.1, but it does not support a 6.1 soundfield, mostly because of (a) above.

d) In general, the more surrounds/rears you have, the less localizeable any 1 speaker is.

I would suggest, that if you have the room, and the denaro, you might just want to jump to 7.1. I had 5.1 for years, 6.1 for about 15 months, and now 7.1 for about 6 months. I kind of wished I had skipped 6.1, but I had to try it to know that I preferred 7.1 more. But I will be honest too, I think that there is a larger difference between 5.1 and 6.1 than 6.1 to 7.1. But I think that in this case, "more is [still] better."