Rockford P3D4 single sub with Alpine MRV-M500, prefab ported box have questions

[Scalian]

I picked up the below Amp Sub, and Box and wired them up in my 2009 Altima. Sub is wired for 2ohm checked with my multimeter. The problem im having is there is pretty much no bass or punch coming through when i listen to rock and when the rap plays it just sounds supper muddy and crappy. Could the box be junk and i just need another one? Would a box make that big of difference. I set the amp gain with my DMM with a 50hz tone to 31.6 volts. Used the whole 500rms x 2 then the square root. One question i have is the paperwork that came with the amp shows 575 rms, should I be using the 575 to figure numbers instead of the 500? Amp is wired with 4 gauge wire. Is this a good amp for this sub?

Im new and trying to read and learn so at this point im needing to start asking questions.

Sub and Box

Amazon.com: ROCKFORD FOSGATE P3D4-12 12" 1200 Watt 4-Ohm DVC Car Audio Subwoofer + Sub Box: Car Electronics

Amp

Amazon.com: Alpine MRV-M500 Mono subwoofer amplifier - 500 watts RMS x 1 at 2 ohms: Car Electronics

Click to read more...

 

[UGHH]

Box makes a HUGE difference. Have one built for the sub, or build one yourself. Never get prefab boxes

 

[UGHH]

If you wired the amp to the sub correctly to 2 ohm, the sub should get 500 watts. Which is fine for the sub, it's rated at 600.

 

[bluemarvin3030]

My vote is box.