Max speaker output is limited by a number of factors, but as a rule of thumb speaker sensitivity +20-23 dB is about the practical limit. So, a KEF LS-50 is about 84dB sensitivity and is capable of peak output put of 104dB at 1M distance which requires a 100W amp. A JBL 4367 with 94dB sensitivity is good for 117dB with 200W driving.
A 3dB increase in sound pressure level requires doubling the power, adding more lower is in general and expensive and ineffective way to make your system go louder. You also need to know the room impacts.
Add 3 dB for a stereo pair, and subtract 6dB for every doubling of the 1M reference distance. The size of the room, and it's acoustics are obviously key as well, but without specific knowledge of the room dimensions and RT60 it's impossible to calculate their impact, other than to say room gain is a function of acoustical spatial loading, and most domestic rooms behave somewhere between half-space and quarter space loads depending on size, speaker location, and frequency. Above 1000Hz, most speakers behave like half-space loads, below 200-300 hz, quarter-space loads. That's all a function of the wavelength of a given frequency. Very low frequencies can't even be made in most rooms, rather they rely on direct pressuring and depressurizing the room.