for kelisa as my gf driving, i also add on a 10" sub in her car, i can say only 10" sub with box can fit in nicely becos if 12" with standard box can not, with small box is waste for an good 12", i will say your choose 10" is right.
if your buget is 200-250 why don get an JVC 10" sub, go check the website, sound good and quality also nice and cheap also, for me at that price i will consider a JVC10" still enaugh for a box. and smaller amp, 10" also better sound acurate,, JVC bass is tight, that is what music needs, i think it is the no1 condenter in its price. hands down kenwood sony. if say you want BOOM BOOM, that go hard way get 15" x2 also can like some people but need alot of modification and big good amp and power supply.
JVC 10" is lest than rm200,
for alpine replica, hey better no for bass, it can not hit subwoofer only for speaker will be ok, go brother there and find one call "Shark" 2 channel amp about rm350 will be good, that is one of the best brother product.
all is my own opinion.