I am pretty much in the same spot as you OP, I am planning on going with Go Go Nihon because they will pretty much take the stress away with all the forms, etc.
When I emailed then, they emailed me a few business days later (like they said they would) and they seem very nice, I also know about some of the mixed feelings about it, I'm guessing you saw Bellatrix Threepwood videos on Youtube? Go Go Nihon also knows about her videos and on a Go Go Nihon Live stream they did back in September they answered questions about her experience and said they listened to her problems and fixed them, so it seems like they realized that they may have not given her the best up to date info, however there was some info she should of researched on her own.
Also about the Go Go Nihon Live Stream, they answered my questions that I asked and they made me even more excited for Japan.
I'd recommend doing the inquiry with them and ask them questions.
Here is some things they'll need from you...
In order to apply for a student visa in order to attend one of our language schools, you must provide the following documents:
-Copy of your passport
-Pages with previous entry into Japan (IF you visited Japan before or will visit before you attend the school, so this is optional)
-High quality self-photo on a plain white background different than your passport (example:
http://gogonihon.com/images/static/form/picture-example.jpg)
-Diploma or transcript from the last school you graduated from
-Bank statement of your financial sponsor (or yourself) showing at least 2,000,000yen or equivalent (So about 20k)
-Payslip, income tax return, or proof of annual income of your financial sponsor (or yourself)
The good thing about Language schools also is the fact that they will help you find a job in Japan, but of course your going to need the 20k because you will only be able to work 28h maximum per week, so don't expect the job to help pay for school, food, rent, etc alone.