They do ok on AM, (I had a MS 700), but they sound terrible on SSB. As others have mentioned, its in the biasing (or lack of it). I have ran a non variable TS DX500 for almost 7 years now with absolutely no problems. Nothing but compliments on SSB, and AM works great as well. I have several different mobile rigs, and the non variable TS DX500 seems happy with all of them.
73,
RT307