Same answer: get efficient speakers.
3 dB is a barely recognizable step up in loudness, and requires a doubling of power. The usual car stuff comes out in the mid-80's in terms of 1W/1m, power input/distance to measurement. So take that at 85 dB, and bump it to 95 and you reduce your power required to deliver SPL to 1/10th.
If you want to get a feel for how doubling things goes, put one grain of rice on a square on a checker board. Two on the next. Repeat until you need an 18-wheeler to carry the next square's worth...
You will not be out of squares.
cheers,
Douglas