sweet deal! what kind of 3-ways?
i'm workin on puttin 3-ways in my doors right now (90' 240) and the only way i can think of doin it properly is by making an entire firbreglass enclosure in the door... lot of work, but it's soo worth it
what you also might want to consider is gettin kickpanels for the 4"s and the tweets... they sound pretty good down there cause they'll be angled up and at your head, and you can keep the 6.5" in the doors cause they don't really need to be aimed.
last thing i can suggest is actually cutting a hole in your door, maybe halfway up where there is room for the magnet and will also aim the 4"s as close as possible at the ears... you should use a bowl of somekind to create a seperate enclosure for it, so that it doesn't use the same airspace as the 6.5"s...
sorry no direct experience with an s14... but these are the only options i can think of in terms of installin 3 ways...