Macallan7,
NOT MANY!!! But most speakers use simpler crossovers, however there are several using outboard large ones, some only take about 1 inductor and 1 capacitor for example, but still is the size of a shoe box. Its not about the part QUANTITY, the Quality parts are far larger. For example you take 1 cap, like a 10 uF cap in a standard Klipsch speaker, its about the size of a half roll of pennies for example.
That same CAP from Clarity or Mundorf, or someone similar and its literally almost the Size of a soda can. So it is definitely not easy or cost effective for most mass produced speakers to implement this for sure. That was not my argument either. Hey I would definitely take a pair of palladiums don't get me wrong, but knowing for 1000 bucks more with such a huge investment already Yes I would build outboard far better crossovers and they would be about the size of a 12" X 16" X 7" amplifier each. And the Palladiums issue with crossover is they are Very complex from what I saw, they are a 3 way meaning a section for tweeter, woofers, and mids, and have about 10 to 15 parts per board. If you use some good ribbon inductors and some Mudorf or clarity caps in that crossover not only will they be that large, but also about 10 to 15 lbs each in weight.
Here is a quick link I came up with on the klipsch website actually
The woofer and tweeter boards alone next to each other although not easily seen in perspective because nothing is next to them as a reference would barely fit next to each other like that on the table in a basic preamp chassis you have on your rack. see link its a cool project to which you can read and check out. Oh and looking back at the link now I do see its the crossover shown next to large Mono block tube amps! Almost the same size. Don't get me wrong the crossovers pictured here are probably 5 times the cost of the palladiums, and they can get much more expensive than even this.
http://forums.klipsch.com/forums/t/103108.aspx