as far as drilling holes in the 340 for mounting them i would think you would want to add some reinforcement on the inside (i think there 5/8 mdf) and also use (not sure technical name ) steal thread inserts and some grade 8 bolts and make sure the mount you would use is overated for the speaker weight. usually better to overbuild something. deff would not want to just put wood screws in there as it prob would chuck itself off the wall at some point
also i would want to make sure this didnt void the warranty. I might email ascend directly about this, since if i can come up with the money, I may try this myself at some point.