well at 19cft and with the 45's you could make it around 18cft (just make them beefy). then with lets say .26 per sub thats .52cft.. which will it make it a total of 17.48cft which should be ok.. after all suggested spl is 8cft per sub. but thats just recomended (please someone with experience with dc subs chime in if im incorrect). so the extra .75cft should be ok for the subs.