1971f + P66 for bottom fishing at 700+ ft?

[AlwaysFishing]

I am planning on purchasing the 1971f unit and the P66 transducer because I want the bottom discrimination function for times that I fish less than 300 ft. I would like to start fishing in the 700+ ft area for rockfish and other groundfish in my local SoCal areas. Would the P66 transducer be good enough for depths of 700+ ft? Which other TM transducers have the Bottom Discrimination function that doesn't break the bank?
If I have to go to the 1kw transducer, which TM185 variety is better for depths of 700+ ft, TM185M or TM185HW? I know I will not have bottom discrimination (major bummer) with these transducers.

TIA.

 

[Johnny Electron]

While Airmar's calculator for the P66 shows the HF will go down to 700ft max; that is best case. I would expect the HF will not reach but the LF (what most call the fisherman's freq) will. Bottom discrimination and accu-fish will stop working about 325ft because of the required beam overlap and necessary angles. Below are the beam angles and max depth for the P66 from the Airmar website.

 

[AlwaysFishing]

Thank you so much!