winter months

So I will have a new little one in November and I'm slightly conflicted as to what to purchase for sleepwear. We keep our house at 70 degrees year round so I know I will put my newborn down for the night in a fleece footie sleeper type deal. After that would you all use a sleep sack on top of that as well or do you use a lighter muslin blanket or what? I know not to put a loose blankets in with one this young so that's why I'm asking what you all do for winter months for the smaller babies. Input appreciated please!