Skar 12 inch sub

I purchased an SDR 12 D4 a few weeks ago along with the prefabbed box that Skar sells. The sub requirements looked to be a perfect match with the box specs. I'm using the RP1200.1D and sub is wired for 2 ohms. Should be 800 watts from amp to the sub according to the amp specs. the Sub may be overpowered a little but i rarely max out my volume.

I was slightly disappointed when i first tuned everything and set gains. The low end I was looking for just doesn't seem to be there and quite frankly some songs just sound like @#it!!! I listen to everything, literally! I can do country today and tomorrow i'm thumping to some hip hop or rap. I love all music and loud. Subsonic is set for around 27hz and low pass is at 80hz. head unit crossovers are all off and i'm using amp crossover. I have a kenwood DPX505BT. It's only 2v preout. Sub volume is up all the way and EQ flat lined. I set all gains with EQ flat lined so I don't mess with it too much and the bass is there trust me. Sub volume is all I need. It gets loud dont get me wrong! But it's higher bass. the box says it's tuned to 32hz but i'm having a hard time believing that. Not sure why they would lie but anyways.

I had a Skar 10 inch tube running off an MTX 500.1D. Was sending 300 watts to this tube and the low end was WAY better than this SDR 12 in the prefabbed box. The tube also uses a port with flared ends and was designed to the sub that's in it. This current box has a slotted vent. Not sure how the two would affect low end. I will say this though. All the systems i've had in the past all had sub boxes that i built according to sub specs and i always used ports. this is the first box that i ever bought prefab as well as the slotted vent.

I am well aware that you get what you pay for and i also know that a lot of pro's and really serious audio enthusiasts HATE skar. What they have suits my needs and is hands down way better than the factory stereo.

So, what i'd like to know is this. Would custom building a box to the sub specs make the sub sound better even though the prefabbed "says" the specs i need for the sub? How about a port vs. slotted vent? I do know i definitely want ported. I don't feel i have enough power for sealed and I don't want to max the amp. I can play pretty damn loud and my headlights don't dim. I drive a chevy hhr so the box is not in a trunk but more like an suv/van enclosure.

Any input is appreciated. Thanks in advance!