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BOSS Audio Systems BX45 Pre-Amp Electronic Car Crossover – 2-3 Way, Fine Tune Your High-Mid-Low Range Speaker Frequencies, Remote Subwoofer Control Included, Equalizer, DPS Audio Processor
Episode EA-AMP-SUB-1D-150 Subwoofer Amplifier with Built In Crossover | eBay
SSL SX310 2/3-way Pre-Amp Electronic Crossover with | Beach Audio
Crossover – SPL
BOSS Audio Systems BX55 2-3 Way Pre-Amp Electronic Car Crossover - Walmart.com
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Klipsch RSA-500 Mono subwoofer amplifier for Klipsch passive subwoofers at Crutchfield
Monoprice SWA-200 Subwoofer Amp - Black 200 watt with Crossover, Phase Control | eBay
SpeakerPower SP1-300 Subwoofer Amplifier: Madisound Speaker Components, Inc.
PSB-300 Subwoofer Amplifier with Crossover / Phase Control – Soundavo
Amazon.com: Acoustic Audio WS1005 Passive Subwoofer Amp 200 Watt Amplifier for Home Theater : Electronics