I am of the camp that says that a Montis + two subs correctly placed and EQ'd is going to beat a single Pair of Summits any day.
Here's why:
The Montis has a very good active crossover for the bass portion that yields very good panel to woofer integration. The single powered woofer, focused on frequencies >80Hz can perform much better and cleaner if not charged with trying to do low bass. The panel is the same as the Summit, so zero diff there.
Two subs, strategically placed in the room (best would be middle of front wall and middle of back wall) individually adjusted with PBK (so minimum a Dynamo 1500X, ideally BalancedForce models), allows for balancing out room modes in the bass region, which when done correctly, opens up the entire frequency spectrum.