Ok so I currently have 2 mtx thunder 4000 subs that are falling apart due to their very old age. My other issue is they take up a lot of my trunk space. I have a 2002 volvo s60 and like to go on ski trips and things like that where I need the space. Because of this I am looking for a single 12" sub for replacement (sealed box). I am currently running the subs off a power acoustik 2 channel amp, 150 watts per channel at 4 ohm(i know not the best brand but i got it really really cheap). I would like this single 12" to reach atleast the same volume level as my setup now. I also dont want to spend a ton of money. I was thinking of getting this Pioneer TS-W3003D4 12" Champion Pro Series Car Subwoofer or this Pioneer TS-W310D4 12" Champion Series 1400W Car Subwoofer they both have high sensitivity ratings. I would rather not replace my amp but i do have the money if needed. Can i run the champion pro off of 300 watts? even though it is rated for 600 watts? I know that is kind of low. I know i am also under the rated wattage for the champion speaker (400 watts) but i am much closer to meeting this. My thoughts were to get the champion pro and upgrade the amp a few years down the line maybe. Any thoughts? suggestions?