Keep in mind that most speaker manufacturers do not accurately state performance specifications, including efficiency (gasp). But assuming that the efficiency ratings are accurate it’s painting with very wide brush strokes and leaves out several important factors like setup, room size, and amp being used. You also need to apply a bit of math to arrive at a realistic output number.
First I’d ask how do you know you’re listening to 90 dB peaks? Most sound pressure level meters are “slow” (averaging peaks/dips versus displaying instantaneous peaks/dips), so under reporting the extremes. Live concert peaks range up to 105 dB for jazz, blues, or classical and 110 dB for rock. Instantaneous peaks can range from 10 dB for rock to 30 dB for classical. These are very ball park numbers, based on venue and where the listener is positioned.
The peaks are an important consideration. Overloading an amp will cause distortion (clipping) that try to force the speaker diaphragm to instantly stop and start, which is extremely hard on it and can lead to failure of the driver. To safely listen you must therefore use a more powerful amp or turn it down below concert levels. Note that continued exposure to more than 85 dB will result in permanent hearing loss and possibly permanent pain.
In calculating actual sound pressure levels (spls) keep in mind that having two channels adds 3 dB, but doubling the distance (from the reference 1 meter) subtracts 6 dB, so sitting 13 feet away would drop spls by roughly 10 dB. That translates into the speaker needing to be capable of producing 115 dB for classical/jazz. If the stated efficiency is 88 dB/w/m (a typical manufacturer’s rating) the amp would have to produce 27 dB of gain (115-88).
The relationship between watts and dB of gain is logarithmic (0 dB of gain = 1 watt, 10 dB of gain = 10 watts, 20 dB of gain = 100 watts, 30 dB of gain = 1,000 watts, etc.), therefore 27 dB of gain equals 500 watts per channel (again to safely handle peaks). Note that 32 dB of gain (1600 watts per channel) would be needed for concert level rock music. Most speakers aren’t rated to handle that much power, so your alternatives are to turn it down or switch to more efficient speakers.
Now before you dismiss all this consider that most audiophiles I know do serious listening to jazz/blues at 80 dB average spl (roughly 100 dB peaks) and 75 dB average for classical (up to 105 dB for peaks) - slightly below concert levels. If you’re in a smaller room and sitting closer the power demands also goes down (saving roughly 10 dB). So bedroom listening at concert peaks could take as little as 100 watts for those same 88 dB/w/m speakers.