should i wire the driver out of phase

It really depends on the phae response of the next cab up in the range. I have similar subs(slightly smaller-but quite close) and they noticeably lose output if out of phase(I can do quick a-b comparison-crossover has phase switch). Try this with your speakers(or do what I did below)

I looked on Bassbox Pro6 at both of my cabs(6th order 18 crossed to ported 12's) and it calculated that both enclosures would be in-phase at the crossover frequency(90hz-actually about 30deg out!) so should theoretically be wired in-phase(which I do and sounds louder)

Hope that helps

 

err...,it'll give you more IF the next box up has a phase dif greater than 90 deg at the crossover frequency,It WILL give you less if the boxes are producing sound that WOULD have been in phase. You can't just say yes it will if you don't know what the next enclosure being used is. 6th order boxes have significant group delay and usually have significant phase shifts,however ported boxes etc also do this-specifically below 100hz. You can't just generalise on this,without knowing more.