I've got a pair G15/150 8ohms in the workshop.
They were in a huge subwoofer cabinet I bought years ago before I knew any better. The seller demo'd them to me in his garage using a sound wave generator of some sort, the sound went so low it was almost inaudible but cancelled out our speech and made the metal door vibrate like crazy.
I used to run a bi-amped rig with a Peavey valve preamp crossover splitting the high and low, through a 200w stereo power amp with the low(left) side going to the 2x15 cab and the highs(right) to a 4x12 cab with H+H pa speakers. The H+Hs weren't great so I tried a pair of 10" 60w McKenzie speakers I had, they sounded great.
Somehow that rig kicked out insane sound levels and sounded great. The Celestions coped fine being used as subwoofers and I could drown out most PAs I came across if wanted.
I'm sure something must've been on the brink of dying but it was abused for ten years with no ill effects, only being retired due to the rediculous size. I prefer going straight to the desk now with a floor monitor.