Does Amazon star rating tell me anything useful for car stereos?

It's a signal, not a verdict. A 4.6 average on 3,000+ reviews for an established brand like Alpine carries weight, but Reddit threads have repeatedly documented suspicious rating patterns on no-name double-DIN units where overall stars are high while sub-ratings for sound quality, connectivity, and touchscreen run noticeably lower. Always cross-check against Crutchfield, Best Buy verified reviews, and r/CarAV consensus.