Hello
I think the 2803 would be the best choice because if you ever need the extra channels you have them. 6.1 and 7.1 are the same. What I mean it is mono, rear center. The 7.1 set-up will be the same has 6.1, but it divides it between two speakers for people who have large rooms and or have to split it between two speakers. IMO I find 7.1 to be more seamless in the rear, and you get a bigger sound stage because you have two speakers. In my case I am going 7.1 because both areas take affect. One, my room is large 30x22x8. And second where the rear speakers are going to be there is a fireplace smack right in the middle of the back wall. There are not alot of DVDs with EX/ES. But as new ones come out there will be more. 5.1 will still be around for a long time to come. There are people who swear by 5.1 and will never go to 6.1/7.1. My suggestion would be get a receiver with more inputs channels, most if not all of the formats, and power. That way your receiver will last for many years until you decide to upgrade.If you have the money take a look at the Denon AVR-3803. IMO the 3803 will last longer than the ones above. Down the road you can even buy a separate amp and use the 3803 as a preamp.
Good-luck
GOLDEN-EAGLE!