I was under the mistaken assumption that there were only a handful of heads with a manufacturer's blessing for 2 ohm loads. (Excluding stereo heads that have 2 4 ohm outputs.) I've just leared Thunderfunk is one. Obviously, I can also add the SVTCL head as it has a 2/4 ohm switch. What other heads will (with their maker's blessing) handle a 2 ohm load - tube or SS?