Looking for help setting up my x-over on my 990

this is what i have: Freq Response 24Hz to 20KHz
4 Ohms
X-Over Ribbon:150Hz to 20kHz
Woofer All Freq Below 150Hz
Sesitivity 86dB
Ribbon 48-inch
Woofer 10-inch
Question is What should my 990 X-over be set at ?
Or would i be better off BiAmping the Woofers to my 990 sub outs and set the Ribbons to 150Hz
reason is after changing from Yamaha/Cinepro to 990/7500 things seem a little Harsh & Forward