Amazon offers the Boss Audio Off-Road Amplified Bluetooth Sound System, model no. ATV25B, for $109.99 with free shipping. That's $10 under our March mention and the lowest total price we could find by $20. It features a maximum RMS output power of 450 watts, 6.5" marine-grade speakers, 1.5" weatherproof tweeters, internal amplifier, Bluetooth, strap, and zip ties.