solo x, sa and dd

Hello....I've recently received a gift from my sister....and now I'm thinking of upgrading my amp and sub....I know what amp ill get me, but I'm struggling to chose between a kicker solo x 12", SA z v4 12" and DD(there's many options in my country on dd)....I'm thinking of the 9512i....I assume these are good subs, pricey but good....I want to put it in a custom ported box, but ill consider a sealed box too....what sub will give the most output while sounding good? Kickers aren't really that good compared to the other two I mentioned, right?...ill only consider buying one of the subs, so I won't have to worry much about space