These
Crystal Mobile come in under your $400 and sound very nice. I have them installed in my car.
Last years model are only $119 from
Sounddomain . Great Buy!!
Otherwise if you want to make your own I would go this route. Some custom fab will be need but well worth the very little trouble!
Digital Designs W6.5 VIFA XT25TG30 DDXO-HP crossover