I'd put stash ahead of BM. BM market is exceptionally fiddly and a crapshoot. Yes BM/Tactician is good, but pretty much everything else is a 2.5 or worse card combo - quarries need mid-turn card gainers to actually do something useful for example. Further, even with tactician there are a lot of other options for having strong megaturns every time: (secret chamber, vault, forge, golem/draw, etc.). It is just harder to get to work well.
Stash, on the other hand, will always allow you to clump silvers for a reasonably strong hand most reshuffles at a minimum.
It works well with a lot of combos:
Stash/Chancellor
Stash/Mint
Stash/Wishing Well
Stash/Venture
Stash/Hunting Party/draw
Stash/Loan
Stash/Cross Roads
It also works as a marginal to decent counter to deck inspection attacks, noble brigands, thieves, pirate ships, and jesters.
This is NOT to say that stash is strong, just that I think the order for the promo cards should be:
5. Walled Village
4. BM
3. Stash
2. Envoy
1. Governor
Governor is hard to play well, but it is just so much more versatile than than envoy. You can easily mitigate the +1 card with any hand reducer (and have a +action built in), the point gain on the last turn with the remodel option can be insane (easily offsetting duchy gains) and gain a silver can be an attack on many decks. Not to mention how well this sucker can feed on itself (KC a Governor to gain a gold, draw it, and then remodel it into a province).