First, I think the 'high' end of model ranges is REALLY soft right now. Last year or two has been pretty much a VERY significant buyer's market. Folks just don't have the cash right now.
Second: Listing in CAD instead of USD, though your native currency, is likely to frighten some folks off. For example, your -66 LOOKS like $14k to me, when in reality it is 10k US. Unfortunately OF doesn't have a way to list in multiple currencies, but I wonder if that makes it seem more expensive than it is.
Third, on a per-watch basis (and tips for when listing it on Ebay), IMO:
Tropical Dial (
https://omegaforums.net/threads/chocolate-tropical-dial-speedmaster-145022-69.173583/): Good looking watch, but at that price, it needs a "stomach drops out" picture. I realize this is probably a watch that is a stone-cold-stunner in person, but it doesn't show it to me in the photos.
CB: (
https://omegaforums.net/threads/105012-66-cb-with-1506-bracelet-and-16-end-links.174143/): Looks more expensive than it is (see above), and the the photos have a lot of glare that I think does it no favors. ALSO: PLAY up the bracelet and the 321! 321 is "hot" right now, so playing up the movement is probably a good idea. Other than "this is old", I don't see in the ad itself (other than knowing things myself) why I would pick this up over any vintage speedy.
Vietnam flown one: (
https://omegaforums.net/threads/vietnam-war-flown-speedmaster-145-012-67-with-provenance.180288/) The history bit is INTERESTING and well presented, I think to someone with a connection to the war, this one should do well. I again would play up the 321 a little more, else I think this is a good listing. From MY perspective, the Vietnam War worn bit scares me away (as it is a watch with a 'history' that would make me not want to wear it), but I think it helps more than hinders.
Transitional: (
https://omegaforums.net/threads/omega-speedmaster-145-022-68-transitional.180737/): Watch looks great at a pretty reasonable price I'd say, though the bezel saddens me(again, nothing to be done :/). Dial photos again have a TON of reflections that aren't doing it a favor (as it is the prettiest part!), but the CAD/USD bit makes it look more expensive than it is.
I hope that didn't offend, I'm legitimately trying to help, and hope you find someone to love each of these. There are 2-3 of those I'd love to pick up if I was looking (holding out on an EW one day...). At the moment, it seems like you need to find the 'right buyer', for at least 2 of them to get anywhere near your asking price, so it is a matter of finding the right collector who wants to grow their collection.