gryphongryph, driving your speakers is something I can't really answer, maybe someone else here is better at the math. Looks like your LS5/9's have a sensitivity of 87dB. My Paradigm S6's are 91dB. I don't have to turn up the volume far at all for it to get very loud, which I don't usually do anyway. Wish I could offer more help.
L.
L.