Let me tell you my plans, perhaps you can use something here. Each speaker consists of:
1) separate box with 2 Peerless 830667 (8" subs)
2) separate box with Scan Speak 15W8530K00 and Vifa XT25 (Zaph's ZD5)
Crossed around 250Hz. Having separate boxes and running them active will allow me to mix and match later on.
Each box has own amp, so active W and active MT (MT has internal passive crossover)
All driven with DIY LM3886 amps.