Hi Sam, don't expect me to answer anything during the day, I work in a factory building systems, I don't sit in front of a screen, waiting for questions to appear.
Anyway, the 6.1 originally had an eminence speaker that I had specially made and a Morrell Tweeter.
The 8.1 had an 8PS21 and a DE12, both B and C. The 8 NDL51, is the speaker I would use now. It's not the obvious one, because the 8NW51 is a Mid Bass unit which is also more more efficient. The other speaker will give you less problems at the x/o frequency, because it doesn't have as much accentuated rise at the top end. If there are other cabs to go underneath these in a system, then tuning will be less important. If they are stand alone cabs then re-tuning will help for max response.
Anything else, just get back to me and I'll help where I can.
Peace and goodwill to all speaker builders
