Well, in general terms, adding a small sealed enclosure should increase power handling and remove some of the low end extension. In realistic terms, I guess this means your doors could get some meatier midbass from being able to dial up the power a bit more to a more constrained range...but the extent to which this occurs is a function of what gear you have, what power is on tap, and what size enclosure you would be making

Sealed enclosures aren't very popular because they have negligible impact...some SPL guys will put midbass drivers in small ported enclosures to try to dial up the midbass in that way (which, if that's what you're after, is the way to go), but they're tricky because they're small and also introduce some sloppiness in the delicate midbass region