Switching it up

I've been running an older Cerwin Vega 15" sub for awhile now.It's 500wrms and in my enclosure(3.34 cubes tuned to 32.5hz),but I'm only feeding it 440wrms(checked with dmm)because it bottoms out with more power.I'm curious if I were to get a pair of 12's,would I gain anything and if so wha?.My amp is rated 2200@1ohm,1700@2ohm,and 1200@4ohm(rms ratings)so I have plenty of power,I'm just curious.If so then some recommendations would be nice.I don't have very much to spend.I usually buy or trade for used equipment to save money.I've thought about a better 15,but then it gets pretty expensive.All opinions are welcome,thanks.
1827d1174615736‑2‑12‑cerwin‑veg
This is what my sub looks like.I'll try and find the specs.

 

http://www.sonicelectronix.com/item_301_Cerwin-Vega+Vega+154+15-+VEGA+Series.html
Here's a link that works.

 

I see that I have alot of lookers,but no input.Just give me some input,I'll take whatever I can get.I found 2 jvc arsenal 12's on craigslist in my area.

 

Thanks for your input.I've had a box in the car tuned to 38,42,and 46hz besides this one,and the lower tuning sounds better to my ears.It sounds very crisp and clean with my sub out at 4/8,but when I put in rap and bump up to 8/8 it's hits hard.I am just wondering how to hit harder.I think my box is too small for 2 12's,but I might be wrong and that's why I'm asking.

 

It's a 2 door '99 Pontiac Grand Prix,port and sub facing the tail light panel(back).I've got it as far back as I can get it.All of the rear speakers are removed and I have a pass through in the middle of my back seat.I thought about cutting the whole speaker shelf out and making a frame to get more sound into the cabin.

 

Here's a couple of subs that I was thinking about:
http://www.sonicelectronix.com/item_8831_Power+Acoustik+FUBAR-15W.html
I would have to find this sub on ebay since it's a old model.
http://www.sonicelectronix.com/item_25402_Planet+Audio+BB15D.html
Any other suggestions?

 

The bass is at +1,no bass boost,the gain was set with a dmm.I really don't know how high it is,but my amp is rated 1200 watts rms at 4 ohms and the sub is rated for 500 watts rms.I turned the sub out control on the h/u at 8/8 to set the gain and my friend did the rest(he knows what he's doing).He said that if he turned up the gain a touch it jumped up to 750 watts.Apparently it's very touchy.My volume was 3/4 on the h/u when we did this.
The only other option I have right now is to send out an old eclipse to get rebuilt.TC Sounds told me that they have 1 aluminum 15 cone left for my sub,it's model # is 8815dvc.It's a dual 4 ohm sub.It's not the titanium one it's just the aluminum one with a 3hp motor.But I'm leaning towards the Planet Audio.

 

http://i152.photobucket.com/albums/s193/bromojr/Forum Junk/Box Designs/Tommy2Tone31432hz.png
This is the design that I used for my box.I don't use loudness and my comps will sound like crap with the bass at -1.I basically set up the controls on the h/u just for the comps and use the sub out for the sub.I've never used bass boost,is it ok to use it?

 

I forgot to mention that this box was designed for 3 10" fosgate punch 10's.I wanted it to hit lower and tried a directed sx12 in the box and now the vega.I made a new baffle and overlapped the old one.

 

Well Ranger,I'll give it a try maybe this weekend.It'll be a couple months before it's warm outside again.

 

I'm going to try Rangers way tomorrow,but I have a question:What is a good starting point for the lpf?Right now it's set at 50 or 60 hz and I like it,but I might be missing out on some sound.