I am not a professional paint or body man, but I have been doing paint and body work since I was about 15. Learned from my dad that has been a professional for 33yrs. He works at a pro shop and and they use PPG and DuPont. But when he does side work he doesn't use those products mostly because of costs. I didn't use either of those product lines when i painted my GN about 3 yrs back and it looks and still looks like any professional PPG and DuPont paint job. I used a product line brand called Big Sky, been using their product for a couple years, really good , a fraction of the costs. I brought everything from the epoxy primer to the clear coat and spent about $600. As far as matching paint, you only to need a base black if it's a GN, so there is no mixing involved.
But yes, I agree with hiboom that you need to use quality products, but DuPont and PPG aren't the only quality product brands out there. The kit you have the link for......I can't speak for that brand, but that is xtremely cheap for a complete setup, I wouldn't trust it, unless you have used it before.