just to be clear... the party pack has a 350w peak amp so 175w rms, plus its running at half power so u end up with at the most an awesome 87.5w rms. (most stereo internal amplifiers are from 68-88w rms)
even at 4 ohms (again half power) that alpine makes 500w rms. sony is more realistic at 330w rms but lets be honest here.... there isn't really an easy way to get that setup "louder"
Assuming the wire you have is sufficient, If you get a 200w rms amplfier your more then doubling the current power that you have now. Don't get me wrong that would get it louder but id guess maybe 50% louder not double the current volume. Problem is id bet that 200w rms would turn those subs into a slow blow fuse. Depending on how you treat it is how long they last. be easy and get the same sound you have now and your looking at a year maybe more. if you really truly expect a difference in sound then you could easily blow them in a few days (hopefully you don't drive very long)
At the end of the day the kenwood party pack is sub entry level garbage and if you truly want more bass then the only 2 options are you spend 100-250 on a new amp thats properly sized but wont give you the bass your looking for and is too small to re-use on anything quality or you spend the 100-250 on an actual big amp and either blow the subs or burn the wire
Sorry but the hard truth is if you want to be louder and you dont want to waste money, your going to need to think of it as everything you have needs to be replaced at some time and plan your upgrades like that
