Assuming that whatever you already have is not satisfactory (if what you already have is satisfactory, save your money and forget buying a new receiver), I think it is worth considering the RX-V663, as it is more "future proof" given that it can decode the new audio formats. Of course, it depends upon what you decide to get in the future whether it will matter. And, of course, which is a better buy also depends upon what the prices are that you can find for each. Since you don't need the extra capability of the RX-V663 now, if the price is very different, I would go with the RX-V661, but if the prices you can get are within about $50 or $100 different, I would go with the RX-V663.