yeah each sub needs at LEAST 450 watts for it to perform well. if you are getting another subwoofer for more bass don't just in vest you money in a 1000 wass (rms) mono block amp. if you liked how your subs sounded before think how they will sound when you actually got the prower they need behind it. if you want to stick with fosgate get the T10001bd it runs 1000 watts rms at one ohm, so make sure your subs are wired up to produce a 1 ohm circuit. i.e. assuming that your subs are 4 ohms a peice wire as such. from the mono amp run a parallel connection (positive from the amp going to both postitves the the box. and do the sme for negatives.)this will reduce your ohm load from 4 to 2. Then inside the box run it parallel again according to hte manual that came with the subs, it should be positive to positive and negative to negative. REMEMBER THIS is assuming that your subs are 4 ohms, find out first. but anyway, all you need is a bigger better amp before buying more subwoofers. i KNOW that you'll like the proformance. and if the fosgate amp i suggested ia a bit too pricy you can find others a little cheaper. just remember either find a 1 ohm stable 1000 watt RMS if your subs are 4 ohms, but if your subs are two ohms buy a 2 ohm stable amp 1000 watt RMS. one last thing if you do have 2 ohm subs you will need to wire it in series from the amp to the box and then parallel inside the box.
sry. the second line should say " subwoofer for more bass don't, you just need to invest your mone in a 1000 watt rms mono block amp." sry 'bout the typo. hope you still understand what i was talking about.