My Is have the ability to bi-amp built in, may try that first using the 700B WOPL, and the PL-400.
External crossover required crossed at 90 Hz or so.
500 WPC from the WOPL 700B below 90 Hz would shake some plaster loose.
The Ohm Is are rated to 1000 WPC (4 ohms) so thats pretty awesome.
I have admired the Ohm Is as a teenager, found a pair on Craigs list when I was 49, replaced the Woofers with OHM factory woofers,Ohm is still supporting nearly 40 year old speakers, very happy with them.