To add just a bit to what agarwalro states above, not only do speakers matter more for the sound than the receiver, but better speakers matter more for the sound than going with 7.1. I would rather have a 5.1 system with better speakers than a 7.1 system with lesser speakers. So I recommend that you forget about 7.1 and go with no more than 5.1 so that you have more money per speaker to get better speakers. Though looking again at the post of agarwalro, 5.1 is what agarwalro recommended (but without drawing attention to it).
Now, if you had many thousands of dollars to spend, then going with more channels might make sense. But I think most people make the mistake of going with speakers that are not very good so that they can have more of them and so that they can have a higher model of receiver. Resist that idea if you want the best sound for your money. Also, in the future, when you decide you need some new feature that you cannot get now, it is the receiver that you will be getting rid of, not the speakers, so money put into good speakers is a better investment in the future than putting extra money in the receiver.