It's right there in the spec sheets.
KF300e page 2:
In biamped mode, the low frequency section produce a Sound Pressure Level (SPL) of 99 dB SPL on axis at 1 meter with a power input of 1 Watt, and shall be capable of producing a peak output of 132.8 SPL on axis at 1 meter. It shall handle 600 Watts of amplifier power (AES Standard) and shall have a nominal impedance of 6 Ohms.
In addition, the mid/high section in biamped mode shall produce a Sound Pressure Level (SPL) of 104 dB SPL on axis at 1 meter with a power input of 1 Watt, and shall be capable of producing a peak output of 134.8 SPL on axis at 1 meter. The mid/high section in biamped mode shall handle 300 Watts of amplifier power (AES Standard) and shall have a nominal impedance of 6 Ohms.
Translation: 600 watts LF; 300 Watts MF/HF - 6 ohm loads for each.
KF300i page 1:
Frequency Response of 65 Hz - 18k Hz ±3 dB;
Axial Sensitivity (1 W @ 1 m) of 101 dB SPL (LF); 106 dB SPL (MF & HF);
100 hour sine wave Power Handling of 250 Watts (65 Hz to 300Hz), 100 Watts (300 Hz to 18 kHz);
If you look at page 45 or 47 of the KF300i spec sheet, you can see they're putting the electronic crossover between LF and MF/HF right around 475 Hz or so.
Translation: 500 watts LF and 200 watts MF/HF
The KF300i is not a passive box - it is biamp only. The KF300ix shows an input plate with a passive option switch, but I don't see on the spec sheet where it discusses the passive power rating - I would suspect in the 400-500 watts range.