Ms basspro-SQ vs 12 inch subwoofers?

Hello everyone I'm in desperate need of help regarding my trucks audio system. I drive a 2002 ford f150 supercrew cab and i do not have a sub installed. I have a new stereo installed that is a kenwood touch screen and claims to push 50 watts x 4. I also have what i believe are kenwod excelon 6x8 front and rear door speakers.

I would really like to add a sub woofer to my set up but I can't fit a big box under my seats or behind them. I went to radio shack to ask around and they suggested a JBL Ms basspro-SQ which is a 300w enclosed 10 in sub. It has the amplifier built in so i guess its easier to install but it is $499.

I'm worried that i will spend all this money and get stuck with weak bass. Really what i want is to be able to feel my bass in a similar way as i would a pair of 12's under my seat. Can anyone with knowledge of this Jbl sub give me advice

Any help is appreciated

That JBL Basspro is simply too large to go under a seat. There's enough room under the left rear seat to install a thinline subwoofer in a cabinet though. You will lose some of the cargo utility when the seat is in the folded position, but that is the trade-off and that's a lot better than the alternatives.

My favorites thinline subs are in the Earthquake SWS Series. The SWS-12X has a very high excursion for a thin subwoofer (unique patented design). It is high-efficiency and pushes a lot of air on a moderate amount of power. The resonant frequency is an amazing 24Hz, unheard of in other thinline designs. It can and will give you what you're looking for in feel without having to build or buy a big ported cabinet. The minimum recommended sealed cabinet is only 19.5"x15"x5.5". The biggest recommended sealed which provides a bit more "bump" is only 8"x17.5"x21". I've yet to have a customer say they weren't happy with this sub. Link to read & watch: http://www.sonicelectronix.com/item_20022_Earthquake-Sound-SWS-12X.html

To that I would trade out your front Kenwood 6x8's for a pair of speakers with a lower frequency response to get better mid-bass. The Kenwoods are only good down to 80Hz. A pair of JBL GTO638's will play down to 50Hz, a significant improvement in the bottom-end mid-bass sound. These are 6 3/4" rounds and you can get adapter plates to fill the existing hole. Or you could go with a pair of 6x9's instead. The JBL GTO-928 or 938 play to 45Hz. The Polk DB691's have a frequency response down to 35Hz and these are my favorites in that speaker size. It may require a minor enlargement to the present speaker holes. No big deal.

Your new Kenwood head unit may push 50 watts peak x 4, but in reality it is only 25 watts rms per channel. It will run any speaker rated up to about 75w rms pretty well. However, you should consider getting a 5-channel amp to power the full-range speakers to their full potential as well as the sub. If you go with the Earthquake 12X I'd suggest the Soundstream T5.2500DL. It will give you the right amount of power at the right impedance for the whole setup. It's a decent quality amp for the price and it's currently on sale from Sonic for under half retail price ($190). For $300 the Audiopipe APK-700.5 would also fit the bill. Moving up the price ladder the MTX Thunder 800.5 is a great $500 amp and I use one myself. At the top of the heap is the JL Audio XD1000/5v2 but it will set you back over $700.

Assuming that you've got a limited budget, I'd go with the Soundstream. That, plus the Earthquake, plus a 6x9 upgrade for your front speakers will total just over $400. Add wiring and materials for a custom cabinet and you'd have a great system for under $500 bones if you set it up properly.