not always true, you could have hella impedance rise with 1 amp, switch to 2 or 4, and have quite a bit less rise, and get more power out of the lower model amps instead of 1 bigger one...
Hmmmmm interesting. Why would one amp have more rise than multiple amps?
more wire spread over multiple subs....
where as, multiple amps have mainly 1 sub to go to, instead of 1 big amp going to 4 subs