To be honest, building the stk-00050 replacement pcb's is a good place to learn, you are having to solder anyways, so whats a few more solder joints. It is the best option imo, that is why I designed it for the community.
I do not know for sure, about STK1050 or 1060, looks like they probably will work based on the schematics, have to verify pin outs, mechanical fits etc. The bias current is now shared between two parallel sets of bjts, so by rights the bias should be increased so that the current through each pair is the same as if using only one, meaning that the V dropped across the single 0.22 ohm emitter R's is now to be doubled from the spec. I do not know if the 780 will allow bias those pairs correctly.
Ask the person who told you it was okay to see what they experienced.