I was contemplating on which i would rather have. I was wondering if i should go with two Sa12s or a single zv3 15. Currently i have a Fi Bl 15 being powered with a Hifonics BRE 1700.1. My box size is going to have to stay around 3.5 cubes because of my limited trunk space in my 2010 Malibu.

So would you guys prefer 2 sa12s or the single 15? 

P.s. I lean more towards lows, would the Sa's get very low?

What don't you like about the Bl?

Specs of current box?

I like the Bl, im just looking to get a little more spl.

I dont think you will see much improvement from BL to Zv3. I would just tune lower if I were you. If you like playing with subs though I get ya, im the same way.  Depending on electrical you could always go with a 3.5k down the road which is where the zv3 might give you the output your looking for