Two or one?
 

Ok so I'm going to start to look at subs and I think I want two slim or shallow mount subs but idk I have a crew cab psd 2002 so I want plenty or punch and then I can beat those ricers in two ways ha what do y'all think?
Oh can I use a mono amp or will I need two or a two channel?

Every real american chooses a cal .45 over a .38.
So first question answered. 2 big guns are better than one!
Sad thing is both questions involve a lot of money.

The slimmer the sub, the less punch it will have due to the less amount of air it will push. I know jl audio makes 10 inch slims that pack a decent amount of punch for their size but they dont compare to a full siz sub. As far as an amp goes, it will all depend on what u choose as far as subs.

I can not agree with the previous statement.
Dimensions do not allow any conclusions on performance or "punch". You will find these performance numbers in the tech papers called efficiency and frequency range.

The sub housing does play also a major rule on the performance. If you go cheap, you can and will ruin the performance of the best available sub.
Sadly enough there is a simple rule. To gain 5% more performance you have to invest 10times more money.
What you want and willing to spend, depends on your wallet. Going cheap is a bomerrang and will leave you disappointed.

As a general rule, a bigger box will sound better than a smaller box. Of course there are limitations to this, but if you have a slim behind or under the seat box with shallow mount subs, you will have better sound out of a full size box with comparable subs. Lets say that a subs optimum range is 1.0 to 2.5 cubic feet, I can guarantee you it will sound much better when it has 2.5 cf versus 1.0 cf.

To the OP, I would go two for sure. Kicker and several other good brands all make shallow mount subs.

Also more thoughts on this. With the slimmer sub, there is usually less travel of the sub due to size limitations (how hard it can hit) and also generally lower power ratings for the sub.

If he want the loudest and hardest bass possible, he needs a good sub in the biggest box in its efficiency range. My 12" L7 is rated for a max of 3.5 cu ft per sub, and my probox is at 2.75 cu ft, and it rocks like no other. IMO, Kicker makes the best subs out there, although I know others will disagree, but I have run everything from their basic Comp speakers all the way up to an L7 on more than one occasion, and have nothing but good to say.

My two 12" Comps (baseline speakers) in the sealed box are an excellent SQ setup, and for the money invested ($220 for subs, amp, and box, all brand new), you cant beat it, so don't say you can't get quality equipment for cheap. Ive had this setup for over 3 years and has run without a hiccup, and hits respectively for the amount of money I invested.

My 12" L7 with the Kicker 750.1 is the second loudest setup Ive heard in person, straight SPL. About $575 for all this.

2 and yes u can use a mono just have to make sure the ohms add up so everything is happy i have 2 10s in mine and its good

I have to jl 10w3's in mine a jl 500 mono pushing them in a downfired box it pounds pretty good

I highly prefer mono amps. Just wire the two 4 ohm subs in parallel and the system and amp will run at 2 ohms. My two Kicker Comps are set up this way, and my L7 has dual 4 ohm voice coils wired the same way.

Enclosure design is 80% of the sound. The smaller box doesn't always mean worse sound. If the box recommendations are 1-2.5 cubes, the 2.5 cubes will not necessarily sound better. It just means that the sub will be more efficient. If the sub is rated at 500 watts, it will be louder off a 500 watt amp at 2.5 cubes than 1. But if you are running 6-700 watts, you can run a smaller box, and still be safe.

There is much to it, but in reality there are a few nice shallow/low airspace requirement subs.

Get yourself a class d mono amp 1 ohm stable, and 2 dual 4 ohm subs and you should be set. Make sure the RMS of the amp is the same or more, than the RMS of the 2 subs together.