Nicko,
I have never tried a FCV-1150 with the SS264 so I don't know how far you will be able to slew the 50 or 200Khz before you start losing performance. Be aware that the 1150 is blocked out from transmitting in the 53-65, 111-139 and 171-183Khz frequency ranges.
As far as I know the 50BL-12HR has a 10Khz bandwidth meaning should perform equally well from 45 to 55Khz.
Snips