651 has been around awhile and has a good reputation. Ask former and existing horses of these stables if you know anyone, that's a good way to gauge. Unless you want to be a robot, verify it's not just a "we give you charts, you sign up for 1-2 years in a contract, and you play for us" type of deal, people often regret those (unless they have the mindset for that and are dead broke and just want to grind a meager wage, which is fine if that describes you).
I've always been a fan of 651 myself. Jackstack is the f'in boss man.
You can also check out my Spins video pack *shy face*. It's got like so many hours of content that you can easily turn it into like a long coaching program for yourself.