I am back into speaker building after a 7 year hiatus, back then LEAP/LMS was the standard for the rich kids and Madisound and Solen were the providers of choice. When Dynaudio got out of providing drivers to DIYers, I lost interest. That plus I got a good job in the industry for a while.
There are many great posts on this thread that should help you.
As far as Ray's links page... I think we have the wrong people doing cancer research, Ray would find the way to have them all licked in a weekend.
The crosover point and slope between your mid and tweet should be more of a result of the tweeters capabilities ad the expectations for playback level. If this is a chamber music playback system for a tiny den, you can use lower x-over points and less steep slopes. A benefit to 6Db or 12Db slopes over more complicated designs for 18Db, 24Db and steeper slopes is that with fewer components, the signal path is shorter and the detrimental effects of each of these crossover components on the signal will be reduced.
For your first ever DIY, you may wish to calculate out a basic first order (6dB) or second order (12dB) and assemble it yourself point-to-point and be gentle on the final product.
If you are going to listen to "Live At Leeds" at the level of the original performance, or use the speakers for HT, then use a steeper slope design and maybe raise the x-over point a touch higher. Get an advanced helper and some modeling and measurement software ad prepare to experiment. Impedance compensation circuits (to keep the crossover point accurate by compensating for the varying impedance Mark spoke of) and bypass circuits are difficult to plan, and easy to screw up.
This is called "voicing" the system and it is an art form.
IMO, don't buy some off the shelf generic pre-fab x-over from the supplier, build it yourself or you may as well just have bought the entire speaker pre-built.
Heed the advice of Colofan and find the local speaker nerds, I used to rap with the PSACS builders here in IL, and long time audio reviewer Tom Nousaine was a regular. Once I tagged along for a private loft sale at Madisound just for the PSACS members, somewhere I still have 2 pairs of 8ohm Vifa cast basket 180mm mid-woofer drivers...
Certified: Vantage InFusion, AMX A.C.E.
Lutron HomeWorks, Lutron RadioRa2 (Level 2)