Now if you have 2 amps each putting out 120 watts/ch it adds up to 240 going into the speaker in a bi or 2amp configuration.
Being a pedant, I must point out that in this configuration you now have 240 amp available to
the speaker. You need to turn it up to 11 to draw all 240 amps.
OTOH. If you buy an amp capable of delivering 240 watts per channel and hook it up in a non-biamped configuration, you are in exactly the same position. You can deliver 240 amps when you turn it up to 11. Put your earplugs in first (unless this is outside on a dock and you are sitting 40+ feet from the speakers
PS: if I were a true pedant, I'd point out that 240 watts at the amp will not turn into 240 watts at the speakers, but that's a whole other conversation.