After you checked the phasing of the mids and tweeters and level matched all the speakers in your set up, check your sub bass by alternating the phasing of the sub at 0 and 180 and see which one blend better with the mids to create that up front stage.
just try both and select which one u prefer. nothing is set in stone in car audio. tweaking all these is part of tuning, to get the most from your system.