EFI Live can be purchased from some of the Vendors here and on Diesel Place or from any of them listed on the EFI Live webpage.
Can you create a tune better than the Quad 215? I don't know. That depends on your knowledge or ability to learn things about tuning with the help of others. With EFI Live you will have the ability to have more, its just whether or not you personally can do it that is the question.
I'm sort of in your same boat except I've already jumped in. I sold my VA Stoopid box (well known to be 470+ rwhp box) in hopes of improving upon it. I'll go ahead and tell you I don't have a single clue what to do to make a tune that can do better but I'm going to hopefully find out. ANd hopefully sooner than later. I'm confident I'll get there because there are lots of knowledgable people out there willing to help you get whatever it is you are looking to get.
ON our zf trucks, they dont benifit the same as a auto truck dose because of a few tables that limit things such as fuel delivery and rpms!! hand helt tuners dont fix this because they dont touch the tables. HTey work on the autos because the tables are already higher or filed in past 3250 rpms.
IMO EFI is way better, but its only as good as your willing to make it! AS Smokeshow said there is lots of help out there from lots of folks!