$200 for a set of crossovers?
First of all, can you just run active crossovers or try bi-amping? Bi-amping should be quite easy and cheap. Run the Silver Flute woofer without the low pass filter. On axis, the Silver Flute can play flat up to something like 4-5KHz and then decays gradually on its own. Since in a typical car your woofers are off axis, there will be a pretty big dip in frequency response starting at about 2.5KHz (up to -10dB depending on the angle, distance, etc). Use a tweeter with just a single capacitor to create a high pass filter for the tweeter. I normally would not like to use a first order high pass filter on a tweeter, but this one has a pretty low resonance frequency. The resonance frequency of the tweeter is at about 1.1KHz, so I would suggest to start attenuating four octaves above, at about 8-10KHz. This may sound too high, but you should keep in mind that you need a high crossover frequency when using first order filter. According to this crossover design web site, here
Crossover Design Chart and Inductance vs. Frequency Calculator(Low-pass), you need a capacitor with value of about 4 to 5uF. I would try this one:
Dayton PMPC-4.7 4.7uF 250V Precision Audio Capacitor 027-230
If you don't have an extra set of amplifier channels for the tweeter, hook the tweeter directly to the head unit amplifier with this capacitor soldered in-line, then level match woofers and tweeters and adjust EQ as necessary. If this setup sounds too laid back, then increase the capacitor value, which will reduce the crossover frequency.
This may look crude at first, but this setup will give you more options for tuning than most passives out there.
If you do want to try a more traditional passive crossover box, I suggest that you try one that's bi-amp capable (such as Alpine SPX-PRO or RF T1/T2 crossover boxes), so that you can adjust the level of tweeter and woofer.