A good 5.25" driver can be crossoved over down to about 80Hz which is low enough for a sub to not be localized in a car.
In my SVT I used the old $5ea 2-way Ultimate crossovers. In the truck I used some MB Quart crossovers that I bought from dnewma04. For my current car when I get to it, I will look to eBay most likely. Seem to have options here and there for under $25/set, more for higher order. I would have used the PE $15ea ones, but now they are gone. Or, may make my own. Haven't thought aobut it much as it will be a while before I get to my car.
