I found one of these for just over 100$ and was wondering if they are any good.

DRIVESINK heat management system
Buffered pre-amp input circuitry
Continuously Variable 12dB Low Pass X-over
Continuously Variable 12dB Bass boost @ 45Hz
Continuously Variable Subsonic Filter (15-55Hz) (Mono Amps)
Direct-connect integrated Speaker and Power wire Terminals
Full Range RCA Line Outputs for easy Daisy chain
RCA configuration
Variable Input Level Control
DC-DC PWM power supply
DC Short Circuit Protection
Bass Remote capability
4 Ω @ 14.4 VOLTS: 1 x 250 Watts
2 Ω @ 14.4 VOLTS: 1 x 500 Watts
1 Ω @ 14.4 VOLTS: 1 x 1000 Watts
SUBSONIC FILTER: 15-55Hz
CAPABILITY: 1 Ω Mono