RCF ESW 1018

It's worth noting that a doubling or halving of power results in a 3db SPL difference. For this sub, 600W ~ 131dB, 1200W ~ 134dB (calculated based on the specified sensitivity of 103dB 1w/1m)

Doubling the speaker cone area by adding a 2nd subwoofer coupled together but using the same available power also results in approximately +3db SPL.

This knowledge is helpful when weighing amp purchase decisions
600W → 1 sub = 131dB
1200W → 1 sub = 134dB
1200W → 2 subs (600W each) = 137dB
2400W → 2 subs (1200W each) = 140dB

In the end it's not absolutely necessary to optimize and match the limits of each component but rather determine how much SPL you need to do the job and what it takes to get there.