It's been said a thousand times before and will be said a thousand times again and again and again.... Sound is subjective so to say that ANY sub sounds better then another can NEVER be proven. That said, I PREFER TREO's SSi line. I look at them as JL's worst nightmare.
As it's been stated, the stealth box is just that, ment for stealth and to fill in the bottom end. You're going to have to figure out what's more important, the SPL/SQ or the room available. I'm not to familiar w/how the Fords are set up, but look for ways you can cheaply mod things. Example, I drive a 2000 GMC Sierra Ext cab, I was able to raise the rear bench seat up 2" to get the extra room I needed to fit the subs I have in a box of worth.