well you can also mod the lt3080 for high current, it has a diagram in the datasheet.
I think a transistor buffer is gonna be a bit quirky compared to 2 identical regulators in parallel but I won't do an analysis, you can probobly dig up dirt on both circuits though.
maybe use 2x of the lt3083's for the HV rails modded, then 2x lt3080's with transistor for the lower voltage rails
but scroll down in the datasheets for lt3080 and lt3083 and look at the schematics
also read the datasheet. THey have something like 80% match with good parts, meaning if you parallel them with a extra margin (cuz its a lab supply), you get like a 60% boost, so 3+0.6*3=4.8A
that means 6 lt3083s will do it, but thats 60$.
if you use the transistor load sharing circuit with the lt3080 you can get by using 2x lt3080 and 2xlt3083
reading datasheet carefully might tell you if lt3083 can transistor shared too. you can probobly also parallel them with the HV mod
Also if you parallel them I think you reduce noise by the square root of devices you add (has diminishing returns after like 4 that are pretty severe). DOn't know how to analyze the transistor one off the top of my head at this hour.