Title says it all 
What I’d really love to know but can’t easily find, is how you compute total wattage and impedance of wiring two speakers together. I assume since you are wiring two speakers in parallel, you add the impedance (2 4 ohm speakers make an overall 8) but wattage… not sure how that works.
I want to build an optimum 2 x 12 for rock/metal stuff, using it with a modeler and the Duncan Powerstage 170 as mentioned. It delivers 170 Watts at 4 ohms. What does this mean for an 8 or 16 ohm cabinet?
What two 12" speakers (with power rec’s) would you reckon to be the best application?
Thanks and apologies if I missed this already covered, I looked and looked before posting.