I bought 2 12" JL Audio 12w3v2 dual voice coil 2 ohms for $150 dollars.
I see them all the time on craigslist for that price.
You can get them, and spend maybe $50 on materials for a nice ported box.
The one I built was 3.5cuft @32hz for my explorer and it sounded really good wired to 2 ohms on 800 watts.
So for a total of around $200 to $250 you would have your subs and box....but you would need to build the box. Which is fun if you take time on it.
I am not saying JL Audio are better or worse then any speaker out there.....I just know from experience that they sound good on 800 watts since I have that setup.
Technically you could get the same Kicker subs you had before....buy/build a custom ported box for them and they would be louder then what you had before.
The sub box you get is going to be the difference here.