I have the Samsung ms650 in my guest room and it sounds great. It has compatibility with the ws700+ subwoofer which you can always add down the road. Without it, it has the most oomph from other soundbars and it can play really loud with no distortion. It also has L C R channels where most are 2 channel. Of course, with the sub price you are then looking at a hefty tag.
In the soundbar world, I wouldn't get hung up on Atmos. It's not their strong suit anyway.
Sony XBR-77A9G / Panasonic DP-UB9000 / Marantz SR7011 / Def Tech 9060 Series