Hi, i do not think having a self publishing company before publishing, or publishing under a publishing company or as an individual really affect the success (sales or leads) of your book.
from experience and research i have made, I got that there are some few basic factors that can affect your book sales when published on an ebook store like amazon and its likes
these are what to consider while thinking of publishing your book.
1. Attractive book cover; even though the popular saying "you can not judge a book by its cover" true? but in reality most readers will tend to stay to check if your book cover only catches their first glance. then they will decide either to move to the next book or consider buying it. for this reason I strongly recommend working with a professional graphics designer who will patiently work with you all through to achieve a good eye catchy design for your paper back or kindle publishing, and you can fined alot of these freelancers online,. I had a very pleasant experience with this designer on one of the project i handled for my uncle when he published his first book. you may want to check her out here; http://bit.ly/gigGAL42
2. Good book titles; Having an eye catchy book cover will cause a prospect to take a second look at your book, but without a good title, they will surely pass on to the next book on cue,. So it s very important to frame your title as much that tells the reader to read more and at the end buys your book for full reading. in doing this you can suggest some few titles on a list and ask critics to help you choose which best tells your story!
3. Publishing Know how; Many young or first time self publishing authors, do not take additional time to make research on mistakes to avoid when publishing or what to do to enhance their sales on kindle and other publishing sites, there are many other stuffs to consider when publishing, things like key word research on kindle search box, good about book description, summery or synopsis among others, for the sake of these you can read more HERE
I WILL HAVE TO KEEP IT SHORT HERE FOR THE PURPOSE OF REPLY, I am new here when am relax I will have to write a post With more factors to consider when publishing your book, I WILL GLADLY SHARE MY EXPERIENCE.