Comparison JL M400/4 vs Rockford Fosgate M400-4D?

[GTBRMC]

Anyone able to give me perspective on the relative strengths & weaknesses of these two seemingly similar marine amps?

 

[David Analog]

Not really a reasonable comparison unless you are just looking at surface specs and surface cosmetics. And RF did copy the JL XD series appearance.
The Rockford Fosgate Prime amplifier is a good entry-level high-value product. A winner for the money. No negatives. It just does not compare to the JL Audio.
The JL Audio is infinitely more performance and sophistication. Advantages of the JL Audio are....
Gasketed cover over controls for marine unit.
Extra transient noise filtering specifically for boats.
More comprehensive input circuitry, buffered pass-thru, and port for remote level control.
Much higher speed analog switching amplifier (Class D) for superior sound quality.
When tested meets its 14.4 volt rating with a 12.6 volt supply. When tested delivers 97% of its 1 kHz rated power across the entire audio bandwidth. Allows you to set the pre-clipping power thresholds with a multimeter because you know the amplifier will deliver the rated power (and output voltage) at a reduced supply voltage.
Plus, much, much more.

 

[redthumper9]

I own two of the RF 400-4D amps that you are talking about. It kinda like comparing the polk db651's vs. the JL mx650's. For most, the RF amp is just fine. I found it has plenty of power for your in boats and I bridged the other to run my HLCD towers. It's small and class D power. For a budget minded system, it's hard to beat since they can be had on ebay for less that $200. With that said, if your budget allows (twice as much), go with the JL. It will produce it's rated power at 12.5v which is around what you'll have in out boats. Build quality on anything JL is second to none. If my budget allowed, I would have JL MHD amps.