I'll send plans for the seven π, seven π-18 and eight π speakers. Each of these includes the crossover, which has been optimized for the drivers indicated mounted in the positions shown in the plans. You can decide what is best for you.Naturally, the seven π-18 with it's 18" woofer delivers deeper response than the seven π with a 15" driver. It has a larger driver in a larger box. The crossover point to the midhorn is very low, so midbass and midrange performance is virtually identical. The eight π is a different configuration entirely, and really no comparison should be made. It is designed for a different price point.