Okay I want to upgrade my factory system speakers. I have a 2004 Mazda 6 with the Bose HU , front and rear door speakers with a single 8' sub in the rear deck. First thing I want to do is I replace the single 8' inch sub that is under the rear deck. I don't want to add a sub box in this car at all. So that being said what would be a good or the best 8' sub to get that can work in an open air setup. I will of course power this with an amp but want to decide on the sub before choosing a matching amp. - thanks