2 subs will give more bass and "potentially" better bass. The most important thing is how you manage them. A lot of things come into play: placement,settings etc. Even when I set up one sub I use "tools" to maximize results. Someone mentioned the need for the same crossover settings which is not neccesary. Most subs can be set at the same frequency and may or may not have the same slope. However there may be a small dip or peak that setting one of the crossovers differently may improve. All rooms are different as are the subs we use. Take the plunge and enjoy. There is a lot of info on tools and how to use them.
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