Not sure if this matches your configuration...
A .68 uF capacitor provides noticeable reduction at 1000 Hz. This is based on 100 ohms effective resistance, if I get the correct idea there is 50 ohms on each side of it.
Screenshot of my simulation:
The incoming signal sweeps from 50 Hz to 5 kHz, to demonstrate the rolloff curve.
I used a signal of 0.2V amplitude, and a DC component of 2V which is 100 x larger (as you state).
The snapshot is at 1 kHz. Notice the scope trace shows the output is much less compared to when the frequency is 4 or 5 kHz.
With the 1M ohm as the next stage, you can use about 200 pF value. The 1M impedance will barely load the incoming signal.