sounds like a really complex and arduous job... when i hook my sub up, i plan on taking the 6x9's out in the rear deck completely. just leaving it empty and putting the speaker grille back on; it will create a discreet port. i have a coupe... and nobody really rides inthe back too often so the 6x9's dont matter to me all that much (althought i like having more midrange and surround). instead of buying 6x9's i can use that money to buy nicer 6.5's to put in the front and possibly some tweeters.