I use the HA DA 1.4 TC with my A-400, but it needs good light.
I'm getting detail in these images because the little guys are quite used to me and they get quite close. I don't use flash....When I positioned my blind and feeders in the fall, I make sure I got good angles for shooting with the sun behind me. I moved the blind a couple of times this year until I got it just the way I wanted.
You can get good detail with the A-400 but you need to be close. The difference between star lenses and the consumer glass, is the opportunity with star glass to get images at distance. That was true until the D FA 150-450 which seems as sharp as any star lens. A little bit of haze in front of the sun is my diffuser.
A-400 images.
The trick with the A_400 and TC is to take lots of images in burst mode. Ignore the AF confirmation, shoot some of th images slightly long, some of them dead on , and some slightly short, change slightly after every burst of 5 or 6 images, some of them will be good.
Of course you probably have to wade through 4 or 5 hundred images, but you get to be real quick at it. after a while.