I have just received a pair of 8341s with a single 7350a sub. This seems to put out more than 10db more than a pair of 8341s alone (108db vs 95/96db). The latter combination would turn red above 96dB). With the sub, I haven't hit the red zone yet. So the big benefit is for SPL and headroom.
In terms of freq response, the room seems to have a nasty mode at around 28Hz. This ends up causing a dip that GLM can't fully correct at around 85-90Hz. This is there with and without the sub. I think I'll need some bass trap management to tame this a bit.
Subjectively, the system sounds amazing. V happy with the purchase