While the local audio shop could be great, my experience with even the "reputable" and highly rated (e.g. YELP) shops makes me think you should investigate other options. Even with shipping, you would be better off going with a box builder on this forum. You can check the vendor's section to see your options.
Are you planning to do the rest of the installation yourself?
When considering sealed vs ported, you have to determine how much trunk space you are willing to sacrifice. If you could go measure the maximum dimensions you can dedicate to the subwoofer (plus a couple extra inches on the plane which the sub is mounted, so it is not firing into your groceries/golfclubs), then we can give you better advice.