Regrettably for me, I've already shelled out for five of the six individual volumes, and had no idea that an enhanced, complete collection would be released. Not sure that I'll quadruple dip (having purchased at least three other complete collections over the years).
I get your dilemma. Purchasing Volume 6 and the Bonus disc probably doesn't cost much less than the complete collection itself, assuming they're both back in print, which ClassicFlix promised they would be, at some point. David stated they will also send casing and labeling for the six volumes and one for the bonus disc (7 disc casing is apparently rather scarce!) for those who go that route.
Good luck!
CHEERS!