I have a Line 6 Spider lll, 75 watt x 2 channel head going into a 4 x 12" Celestion modeling speakers, which happen to be the most expensive ones they make and the sound is outrageous in Stereo! I bought this back around 2005 and it has not moved from it's original position, thus it is still functioning as new, imho!
I turn it maybe to the 10'oclock position and it is quite loud, but not enough to feedback unless directly in front of it.

I also use a Rocktron Vendetta 4 channel 100 watt EL34 power tube x 5 12ax7 JJ Tesla preamp tubes amp head into a 4 x 12 Vintage 30's and Heritage 30's in an "X" pattern which gives it a "3-D throw" with an A/B box so I may run both amps at the same time and what a sound!!! I am 55 now and Retired, so I only play at home for My enjoyment with Friends and been playing since 1968, so it's been a Journey!