The 1/2/3 would be hard to find, especially with a working equalizer (aka analogue bass computer).
The Five and Six are both well regarded. The crossover in the Fives is fairly complex, and will cost $60-80 in parts to rebuild (for the pair)....but of the three pairs I've restored, all benefitted significantly.
If you consider the Six, be aware that there are three (some would say four) versions, as follows:
1. The original version, in which the grill is glued to front of the speaker and the woofer is glued to the front baffle. This woofer has no basket, and cannot be removed. As a result, getting to the crossover will be quite difficult....you have to remove the backplate and chip away the epoxy in which the crossover components are buried. You can identify this version by the glued on grill and by a back plate (with the speaker terminals) which is flush to the back panel of the speaker.
2. The second version, with removable grills and a "normal", removable woofer. You can remove the woofer to get to the crossover components, but again they are buried in a hard epoxy which has to be chipped out. In this version, the back plate is again flush to the back panel of the speaker.
3. Same as the second version, except the back plate is inset (rather than flush) and the crossover is NOT buried in epoxy. There is a later version of this one with vinyl rather than wood veneer; they were produced at the very end of the long production run for these speakers.
To me, the three-way Five has a fuller sound than the Six, goes a bit lower, and can handle more power. The two-way Six, on the other hand, is a bit more detailed than the Five.