For about two weeks I have been using a ICOM 705 with a XIEGU X125B amp on HF and DSTAR HF Voice. The PTT/ALC line out of the 705 is just a 3.5mm Stereo plug. Tip and Barrel is the PTT line. Pin 2 and ground is the keying line on the 125B. I took an old mouse mini6DIN cable to get Pin 2 and ground out. The 125B manual has stern warning about using high setting to the PTT line. The 705 comes set to low. 1 watt from the 705 on 20m gets about 100-105 watts out of the 125B. The 705 has output voltages to make autotuners tune. The 125b autotuner takes input voltages to move from band to band. However, they do not match. So you have to push the manual band select as you change bands. The size of the 125B is just about .5in larger than the base unit of a 7100 or 706. It does not have any fans. And is limited to 55C. Takes about 16 amps to get a little over 100 watts out. It does work. I don't have any spectral review or such. But good audio report I have received.
Down sides - No fans. I can get near 55C running DSTAR HF Voice at 100 Watts on 20m.
Output varies wildly on different bands, requiring increasing, or decreasing the output power on the 705.
The manual says to tune the 125b auto tuner with the amp in standby and send 5 watts to the tuner to tune. That does work, most of the time. You switch the amp out of standby and on at 5 watts in, the 125b shuts off, or gives all kinds of funny warnings. Remember it takes only 1 watt on 20m to get 100 watts out.
It is not an Elecraft KPA amp. A 100 watt amp with auto tuner for $550 is reasonable. Years ago, when I bought an ICOM AT-180 auto tuner for my new 706, I think I paid over $400.
I have used ICOM 7300s, great radio for the price. I have 2 7100s. And a 7610. What I desired was a ICOM IC-7150C, a upgrade of the 7100 with color screen, DSTAR, SDR Receivers, waterfall, Bluetooth, Wifi, builtin GPS. So the 705 with the 125B is the closest I have got.