1) that sub you have is ok, if your'e looking for more bass you can add another sub or buy a better sub-like RE,FI,SSI,Etc......
2)why do you want apline speakers??
there higher line is good but dont buy the R or S line, they arent worth the money.
3)Since you live in Oakland you can drive to Hayward,Fremont,San franscico,Marin County, to listen to Morel,Dynaudio,Zapco,Hertz,Focal,Boston,Rainbow,ID,Genesis,audison,Etc....
we have so many choices locally that we can compare to.
4)take your time to do it right, so you'll know what your ears like, then when your;e ready to buy you'll know what you want.
5)Quamtum Bass Processor????
does it really help???
What is your amp xover @,is your box sealed or ported??
is your bass boost on or off???
is your subsonic filter on or off????
since you have a 400 rms sub, i wouldn't add 750watts to it,
what is your bass settings on your deck????
do you have your xover on your deck on or off?????