This was what I ultimately ended up with: a micro ATX gaming rig that's very nearly silent.
After three consecutive pumps died in as many weeks in the AIO water cooler I was using, I'm back to cooling with air and the new Shadow Rock LP CPU cooler is doing a good job of keeping everything quiet and reasonably cool.
My H77 motherboard developed an annoying case of coil whine (or maybe it had the coil whine all along, and I only noticed after putting the parts into this quiet build), so I swapped it out for an Asus Maximus V Gene, the motherboard I probably should have bought originally. I found one fairly cheap on eBay with bent CPU pins, fixed the pins using the mechanical pencil method, and I'm in business.
My GTX 970 was not quite up to the task of pushing 3440x1440, so I bit the bullet and (painfully) spent the cash on a GTX 980Ti. I chose the reference cooler model, since many people suggest using blower-style coolers in mATX cases. It's a pretty good cooler. At idle, I can't hear it at all, and while I'm gaming it's very quiet and makes more of a "whoosh" air moving sound than a whiny high-pitched fan sound. So I'm happy with it, and if it comes down to it, I can always try swapping in one of the EVGA water blocks.
EDIT: I added one of the EVGA Hybrid coolers, exhausting out the top of the case. It's a tight fit, but it keeps the GPU nice and cool.
I could probably improve airflow further by moving the radiator to the back, but it would interfere with the CPU cooler in that location. I'm not 100% happy with the layout in this case.