Definitely avoid B and E. I'd probably lean toward either C or D for positioning, assuming the center of the speaker placement is also the central listening position. While it's true that the lowest frequencies are omni-directional, somewhere around 80hz localization starts to occur. That's why the majority of AVRs default to 80hz as the crossover point, regardless of speaker size. It looks like the Sonance satellites and sub have a 100hz crossover, which could cause some minor localization. Additionally, you want your ideal listening position to be relatively equal in distance as the sound will travel at roughly the same rate. Position A would likely work well for the center of the pool and from left to right. However, you might run into timing problems if you have any seating that would be in back of A. I'd also worry about resonance with sound coming off the house.