The Juggernaut is 19.8mm Xmax, so take care where you get parameters from, the manufacturers recommended box internal volume is best but if you need lower volume like 4 cubic feet you should be fine, you can use the model you entered and lower the volume to see the effects.
Other than that there are many subs out there if you are not set on that brand, from the parameters looks like the juggernaut is higher efficiency with higher cone area and lower MMS, which means it will get louder for the watt, to that end the larger box will help.