Well, I own a lot of books on speaker design and have done a lot of research designing my own speaker.
If you google crossover calculator you'll find applets and charts for calculating all sorts of xos and tons of info on the subject.
Basically, the smaller the cap the higher the xo point and with one cap you get a 6 dB/octave slope, so for a super tweeter you can simply raise teh xo point in order to attenuate output rather than use resistors, which add another part between the amp and driver. In your case it ultimately doesn't really matter as you'll have to experiement with cap values to get the sound you prefer and I'd agree w/Roscoe that you'll probably find a good balance around .3 uF for your setup but it depends a lot on personal preference.
I've grown to like the approach of crossing the tweeter over high to match levels rather than pad down with an l-pad. You effectively extend the range of the tweeter's top end. However, this presumes a well-behaved tweeter. You may also find that you can use a tweeter of lower sensitivity if you cross it over high enough; this opens up the universe of excellent "supertweeters".
I'm using this approach with a pair of Altec's I own. The 414A is run without filter and the 802D is brought in at 8khz with a single capacitor. No other components are needed.
