I think we should now lobby Sound United to offer FW upgrade to add the full/true pre-amp mode to the X/4400/4500/6400/6500H and the SR/6012/6013/6014/7011/7012/7013. At the minimum, a paid upgrade, if kept under $30.

I have seen the schematics/block diagrams, the switches and relays are there for those models (the X4300H and SR6011 may be okay too), not a hardware issue at all.