I'm so happy I finally decided to add an amp to power my Polk db series speakers in my truck; it makes a world of difference in the sound quality, especially in the amount of bass added to my front stage. I went with this amp because I needed a small amp in the 50-75w rms range that would fit under my seat. This amp does not disappoint! I knew it would be small, but I wasn't prepared for how compact this little thing would be. Even with this amps small size, heat is not a problem. This amp is Class D, so it runs very efficiently, and therefore very cool. It just gets warm to the touch and has plenty of power for pretty much any system. The amp sounds great, although there is slight distortion at zero volume, but once music is playing this sound is inaudible (this distortion is probably more noticeable because I have 2v preouts and have to turn the gains a little higher than if I had 4v ones). Build quality is extremely solid and I expect this amp to last forever, my only gripe is that controls on top are a little flimsy, but this isn't a big deal at all. Overall this is a great little amp. If you're in the market for a small and powerful amp look no further than the R400-4D.

Handles everything and can push T1675-S's and T165's quite nicely. After not using the gain as a volume control and setting it properly i could push the speakers to there limits with clear highs and lows and no distortion.

Once again Rockford does its stuff. This amp is a monster and runs my Power 6x9s and 5 1/4" components extremely well. They aren't monster speakers by any means, but this amp keeps them perfectly fed at 75w to the components and 100w to the rears...very, very loud! Keeps the music as loud as and clear my subs keep their bass, which is nice because now I can actually hear the music rather than bass alone.

If this is what the new prime series is offering I couldn't imagine what the new power series is going to offer. Got this amp pushing a set of t2 components and a set of 6x8 primes and wow sounds way better now. Had a Rockford PBR300x4 but it messed up? Sonic was quick and great on the return if you plan on getting the PBRx4 just spend the extra $15 and get this great choice on my part.

has the power, quality and runs cool, but it lacks in the mid-low range frequencies.

and to the guy who says he was only using about 15% of amp power u need to learn the gain is not a volume, it is used to tune the amp to the radio outputs, higher voltage = lower settings, lower voltage = higher settings

Clean, clear, and loud. Great amp. I'm using it to power 4 infinity 6.5 inch two way speakers in the radar arch of my boat. Factory tested at 502 watts RMS. The only amp I have that is better is the R600 (same amp more power). Definitely go for 2 guage wire and a second battery if your getting more than one.

i bought this amp to power my t2-652s and spr-17c. this amp delivers and then some. for the price and power this amp puts out i def. recommend this product. i have been a fan of rockfords amps and speakers since i started building my audio system. they deliver top quality products. especially there prime amps. the size is another plus in my book. i have not have any problems with this amp or any of rockfords products. to put the icing on it all ,sonicelectronix prices are especially why i keeping coming back to buy more products!! thanks!!

Had this hooked up to 4 rockford fosgate T1675's that say they handle 75 watts rms each. this amp puts out 75rms X 4 but i had the gains on 2. 2 out of 11 and was insanely loud. Anyways, speakers started sounding very bad after about an hour and the amp started smoking really bad. keep in mind that i was only using about 20% of the amp capability so i was only putting around 15 rms to each speaker. i have been hooking up stereo systems for 15 years.

AWESOME AWESOME AWESOME AMP!! Produced way more power than it was rated..LOVE the amp...thanks Sonic!!

I purchased one of these and had it hooked up to two pair of 6.5 Pioneer components for ABOUT 15 MINUTES and it completely fried itself. I'm not sure what to say about this other than the RF quality control is not the same as it used to be. I have had several RF amps in the past and never been disappointed until now. The up side is that it failed immediately instead of 13 months after purchase. Sonic was great to work with and they hooked me up w/a RMA to get my money back. I replaced this w/the JL XD400 and it blew this thing out of the water; no comparison. However, the JL amp was more. All that said, you get what you pay for. Do not buy this amp *unless your only pushing a pair of tweeters.