well, IMHO, the 'best' is my Subbits subtitler. (But i'm biased, as I'm the developer.)
It can do subtitles from scratch, but there is also a nice Premiere helper app. that gives you editable titles in the timeline / bin.
Have a look here:
https://www.youtube.com/watch?v=FcKOZAkhRRM
To download a demo to see for yourself, go here:
https://www.videotoolshed.com/product/subbits-subtitler/
Note, you have to make your own settings in the Render Engine to get a box.
(It's not something I personally like, so there are no presets, but it is possible. The box opacity is set to fully transparant by default, you have to up that.)
You may mail me direct if you have specific questions, but over here is also fine if others might benefit.
hth,
Bouke
http://www.videotoolshed.com
