Why not ask on diyaudio forums, the crowd here is not into speaker/cross-over design??
2 responses Add your response
First step is to find the right woofer.
You might benefit from the flexibility of a Behringer DCX2496 and play around until you get the sound you want. See this thread.
Alternatively, I 'd suggest to contact Wilmslow audio in the UK they have a design mated to Volt Woofers(Wilmslow Prestige) and another using ATC woofers(Wilmslow K100).
If you are really using two ATC "S" type mid domes then I can only assume this is for live venue sound reinforcement or an extremely large space. IMHO, You should plan to build enormous cabinets with four ported compartments and four Volt RV 3143 Studio drivers (similar to Quested type designs) per speaker. Anything less is unlikely to keep up with the two domes and it seems a waste to have that much midrange output but be unable to use it for lack of bass SPL output.
If you buy a lot of gear from Wilmslow then I'm sure they will help you with a solid sensible design. If you have all the kit and just want advice then I doubt they would be as helpful (nothing in it for them).