I haven't followed updates about the crake, but Bigal seems to be a very good place if you are trying to see the Wood-rail. I don't know what the hit rate is but it seems regular enough for me to consider Bigal on my next itinerary to Ecuador (ofcourse Bigal should be on the itinerary for like 10 other birds!)
I can only guess what the target birds are (therefore my open question), but if you are after a good number of the more common stuff, you can't go wrong with the classic destinations where you will see an excellent set of tanagers, hummers, anpittas, antbirds, (mountain)toucans etc. Only if you are after species like the ones mentioned by Josh, you would have to search for more specific info, contact local guides, contact birders that have recently seen those species etcetera. And even then, most of those species can be very hard to see and are not very reliable.
ps: ouch, Josh, I thought I only had one bangsia to go (Blue-and-gold), and now it seems I have to get Yellow-green Chlorospingus as well!
ps: I would consider Esmeraldas Woodstar as part of the Southern circuit.
ps: of the list Josh mentioned, I have seen 3! Black-breasted Puffleg, Cocha Antshrike and Ochre-striped Antpitta. I kind of 'tried' to see Black Tinamou, Banded Ground-cuckoo, White-rimmed Brushfinch, Orange-eyed Flatbill and Andean Laniisoma. All others were either not 'available' on my circuit (Chestnut-bellied Cotinga, Esmeraldas Woodstar), no sightings (Red-winged Wood-rail, Colombian Crake) of simply no luck. That was 10 years ago and my first trip to the neotropics. Since then, lots has changed but at the same time, lots is still the same.