The original poster's complaint about the TS-570 is RF power spiking. The TS-590 suffers the same problem and is a no-go.
And so do pretty much most radios on the market to some extent or another.
The power spike problem on the TS590 can be mitigated in one of two ways:
1) Go into the service menu, go to the ALC Reference (I think its menu 23) and LOWER it to around 113 so the ALC is active all the time
2) Use an external ALC either from an amplifier or as one person did, homebrewed using a battery and a variable resistor.
The TS-570 is absolutely horrible for 160 meter CW contesting while the K3 is ideal.
And the K3 is absolutely horrible for SSB whilst the TS590 is ideal.