Which end of the sealed box recommendation to go with?

Hi all, im new to the forum and this is only my second post... I currently have 2 old school visonik 12s and a hifonics hfi1000.1d on 4 awg wiring.. The hfi1000.1d is a great buy... btw... but the box im using is 1.5 TOTAL cu ft. and the specs are anywhere between 1 and 1.5 cu ft. PER SUB... So my question is which side of the sealed recommendation should i go with? 1 or 1.5 per sub... i have enough room for either... just want to know which is better... thanks in advance...

here is what they are... Old school... but they hit rather well really... even in the tiny box

Visonik V126S4 12" 4-ohm Component Subwoofer at Crutchfield.com