Breaking 140db?

I thought that might be the case. If I were you I would download Winisd (free!) and play with that. Model up some woofers to your specs. You will need to choose wattage, but since you have neither sub or amp, go based upon the woofer's rms power handling. 

I've been playing with it. One question I have is on the "Choose Alignment" part just before it goes up on the graph. What are the different alignments about?

Pacific. It's 11:40pm.

Well, I'm only going to have this truck as a daily driver for a couple more months. Then it'll just be a car to mess around with. And there's so much ignorance and bullsh*tting that goes on at my local car audio shops, I really want to bring something down there and show them that MTX isn't the only brand that makes subs, and a single 12 can infact be damn loud. The other weekend, I was down at one of them, and the manager brought me out to his car so I could hear his two 12" Type R's. Then I brought him over to my truck and put his subs to shame with my single 12" Type E. It literally left him in awe that the dumb 16 year old kid that he's always trying to sell bullsh*t products to beat him. After that, he got extremely nice [and stopped trying to sell me all kinds of overpriced useless crap], and started offering me deals on just about anything I wanted.

First off, unless he had some type of crazy ass enclosure I dont see a type R ding a LEGIT 138 off 350 watts rms unless the mic is spiked a little. As for your situation I think that 2^3 feet is enough for a ported enclsure for most subs, but if ou can figure out anyway to get 2.5^3 you are far better off. I am not quite sure what you have agains MTX as I have found they are one of the best SPL subs avalible in their given price range. At least outta whats avalible locally. That includes, but is not limited to, Pheniox Gold, Rockford, Concept, Boston, Eclipse, MB Quart, Alpine, Focal, Kicker, Pioneer, Kenwood, MA audio, JL Audio and Cerwin Vega. But as for other options besides the MTX stuff, Kicker L7's are made to be damn loud and have still been the center piece of some of the louder single sub vehicles I have been in, higher end eclipse stuff is good as well. I wont recomend a JL of any kind for spl use because there are always several alternatives in the same price range that are usually a better option. If you want some honesty now here it comes, be prepared to spend on this. If you wanna achieve a LEGIT 140 not a spiked mic 140 but a legit 140 off a single 12" then its gonna cost you. Your not gonna do it with a 150 dollar woofer in a truck with that kinda airspace. If I had to place money on anything doing it I would probally be putting my money on the MTX 8500, Kicker L7 or Top End Eclipse. Problem is I am not sure on the mounting depth of those 3 woofers and whether or not they will even fit. I tried to help a little but I have to actually doa  little reserch on this. All this was just off the top of my head, but I have been doing the sound off thing for about 5 years now and I very rarley see a vehicle do 140 with a single 12 in a regular truck.double-secret reverse-osmosis speaker-cone-induced high-level interference distortion, Its a killer

Oh, no. I definitely don't have anything against MTX. One of the subs I've been considering is the 7500 (I believe 8500 is too deep). I just meant that in this town, there's two car audio shops. And you'd be hard pressed to find one employee that really knows his stuff. Most of them think the only sub brands even worth a glance are Alpine, MTX, Kicker, and RF (the only brands they cary). None of them have any idea what the hell RE is or Adire. I mentioned putting a Shiva or two in my next car because it will be more of an SQL setup more on the SQ side, and he had never heard the word "Adire" before. He told me I had better go read some reviews on that company and sub because I would probably just be "throwing my money away".

ive done a 149.5 on the new mic... single 12" 1250 watts.. re se sub  box was 3.5 cubes though.. dont be a pet monkey ..use your dmm