When I look in the QST review of TS-590 and IC-7600, the TS-590 is in average a bit better!
IC-7600 ( 3rd/5th/7th/9th order)
Worst case band: HF: –31/–35/–41/–48 dB;
50 MHz: –31/–34/–45/–55 dB
TS-590 (3rd/5th/7th/9th order)
Worst case band 10 m: –29/–32/–42/–52 dB;
6 m: –34/ –34/–48/–56 dB
As you see there is no real difference between that two rigs for TX IMD. But the TS-590 RX is much better!
73, Peter - HB9PJT